Wow!! I had many similar tendencies when I was 6-12! Some have persisted even to now in various forms though. I will share all of the ones that relate to yours before sharing some of my "unique" ones.

Your order of 1221 2112 2112 1221... IS EXACTLY WHAT I DO!!! If I touch something with my right hand, then I must touch it with my left to be fair. But then, my right hand touched it first, so I must start another set of touches where my left touches first. But then, my right hand still touched it first in this new sum of sequences! So I repeat again starting with my left hand. This would apply to everything, and I still sometimes hum it mentally using two different pitches. I overcame the compulsion by learning to accelerate my touching and result in both hands on the surface simultaneously. I reasoned that this would be infinite touches, and that any consequence of excess touches would be dwarfed by the immensity of infinite touches. Now I have no desire to work this pattern into physical actions. My familiarity with the pattern brings me joy now, as I'm really interested in fractals and calculus. This sequence is called the Thue-Morse sequence, and it is the fairest sequence I can come up with.

If something is loose (like a handle of a cupboard), I would get irritated because it has to potential to be jarred more times in one direction than the other. It is another variable to be concerned about. I would thusly try to tie my shoes as tight as possible. The same tightness was important as well, to preserve the symmetrical look.

I used to keep all sorts of things like clothing tags and candy wrappers because I felt intensely sorry for them (good thing my sympathies never quite stuck with organic waste), and rocks that I kicked down the road were no exception. I still probably have a few of those rocks lying around from when I couldn't let them go.

The one where you make your feet hit distant objects... I have similar things with impossible tasks, and when I don't feel like I spent enough effort in concentrating on it, I will fail myself and feel awful.

I have the exact opposite sentiment about sidewalk cracks. I had to avoid them, but in addition, I had to traverse each concrete block in the same number of steps.

Your pressing of all the remote buttons in standard order very hard until you feel satisfied is completely understandable. You lose track of how to correct it (and eventually feel that even correcting it is not good enough because it has disrupted the concept of "the first time an action is done is more important than the second" and the corrections don't 100% make up for the error) and decide to just overwhelm your thoughts with infinite pressing so that you can start over because you still have to do it. I have the same kind of resetting behaviour for most of my symptoms.

I also had a blinking problem. In addition, I used to shake my head to flick the hair out of my eyes. I had to keep feeling the slightly dizzy, brain-against-head feeling. This would result in 5-17 head shakes about 1-3 seconds apart. This has made spontaneous reoccurances (once even in grade 12). The annoying part was that due to the direction of my hair part, the shaking only occured in one way. Sometimes I would kind of shake my head back and forth just to satisfy the evenness a bit.

When I was scared of things (sometimes my brain would just invent scary things. Dead bodies are terrifying), I also had see everything, by line of sight, or by mirror. This made shampooing really scary. After watching Grave Encounters II, I am still scared of opening a door (especially elevators, like in the movie, which only have one way out) and seeing a scary place.

I think I understand why you fear planes crashing into the house when thinking about audio recorders. I believe that correlations between things will happen, regardless if they are causal or coincidental. It is this and the fact that I irresistably scare myself when I consciously don't want to that things like this arise for me. I would probably fight myself in my head while mentally humming the 1221 pattern.

For the candy thing, it's only with candies that I hold in my mouth for decent lengths of time. My cheek changes in texture, which I find an irresistable need to balance and/or chew on. I chew all my hard candies now.

When I was 2, I cried for no reason, stating that it was because I just felt like crying. My parents were bewildered. They probably don't remember this though. I have definitely cried for the sake of it more times after that. It makes me wonder sometimes if any crying I do is real because I tend to exaggerate my own emotions (I suppose to validate that I have them, which is silly). I can stop crying 99% of the time, which concerns me a bit.

Now I'll list most of the things I consider less directly related to your stories:

I imagine that bad things will happen if I do not meet a criteria (I still do this now). For example, if I do not make it to the elevator in 7 steps, my girlfriend will die (I usually think of some pretty bad things, but it's like when you're in the dark and you try not to think of scary things, but you can't help trying to imagine the worst). In response, I usually pleadingly think "just kidding!" multiple times, but always in an odd number so that the negations don't cancel each other out and leave the original problem of potential failure. Sometimes I even offer a consequence of less magnitude that I am more comfortable with experiencing.

I will read something over and over and over again until I have grasped it at an overly complete level. Even now, when I watch foreign shows, I will sometimes rewind to make sure I have recalled reading every last word of the subtitles. If I read some words more than others, I will get frustrated, knowing there is almost no way of keeping track of which ones I've read more than others, and will probably perform resetting behaviour multiple times, resulting in pausing the video and reading the same thing a lot.

Cleaning habits (that one disappeared fairly quickly): I would wash my hands, and then wash the tap, then the doorknob, so that I can keep my hands clean when exiting the bathroom. If I didn't I would be compelled to wash my hands again.

If something protrudes (such as my nose, or my toenails), I really did not like sliding it against the pointy end. If I rubbed something on my toenail in the direction of my ankle, or rubbed my nose upward, I would have to rub it the other, "smooth" way many times to smooth over the feeling that I had disrupted a smooths surface.

I would imagine that my feet had imaginary straight lines coming out of the left and right sides, and from the toe and heel, extending horizontally. I would be compelled to avoid having these lines be trampled by heaving moving objects (mainly cars). I would have to angle my feet so the line sank under the ground, so the car passed over it.

I would also imagine a line coming from my body (like Tron), but it was flexible like string. If I entered somewhere, I would have to exit in a way such that the line would not get caught on anything on the way out. If I walked around a pole 8 times, I would have to untangle the line by walking around it 8 times the other way.

I would feel a slight projection of my "aura" out of my sides, and if it got caught on something (any object, really), I would have to smooth over the disruption by doing something similar to the smoothing over thing I described earlier.

I hate getting any part of my body sticky. This is what made apples and other unsliced fruit annoying for me. Stickiness resulted in immediate hand washing. Don't even get me started on maple syrup. It gets on places you're sure it never touched.

When I was little, I was obsessed with rainbow order. If I had an orange and a green duotang for example, I would get made because not only did it not start with the first colour (red), but some colours were skipped.

I am an intense perfectionist myself. But having failed so many of my behaviours (we can't do 1221 forever, can we?), I kind of developed that resetting behaviour, which serves as a kind of a cheap workaround. I feel like I constantly fail and put zero effort into things because there's no point in starting such a potentially imperfect task. It could also explain why sometimes I give up thinking about something because I just dismiss it as too complicated, and make rash actions. Other times, I will think agonizingly before making a decision.

I am really glad I've found someone who has/had similar urges. Cheers! Make an account here and PM me if you want to discuss! I've been through some of this in some degree and have never had a psychiatric evaluation.