Hello, I'm here because I desperately need help and advice.
I think something is mentally wrong with my 2, almost 3 year old son. This post will be quite long and I'm sorry for that.

When he was born, he was a very happy, but picky baby. He had to be close to me all the time (his mom) and would cry when held by someone else.
As he grew, it was obvious he was very smart and could pick things up quickly. He started being hard to control by around 18 months of age. He quickly figured out how to open (and unlock) doors , how to climb out of his crib, how to climb over the baby gate etc. This meant he got into everything.

Just before he hit two, the tantrums started. I figured it was the terrible twos starting as his older sister went through the same thing around that age. The problem is, his tantrums are completely different. It's almost like he'll find anything to have a tantrum about. I'll explain using an example.

When put him to bed, we (my husband and I) give our kids a 'cuddle and a kiss' goodnight. When we go to do so with my son, he'll say "No cuddle and a kiss!" so I used to try and use reverse physiology on him and I'd say something like, "Fine, no cuddle and kiss for 'Adam' tonight" he'd then of course get upset and want one. Well, the problem is he figured out this game and now uses it on us, but for EVERYTHING.
Now when we put him to bed I'll say "Give me a cuddle and a kiss." and he'll shake his head no. So I say fine, and go to leave, he then wants one, so I would go to give him one and again, shaking his head no. I'd go to leave, he wants one.
Well figuring I wouldn't put up with this, I'd tell him to give me one at night and if he said no, that was it and I'd leave. Well, then he would have a tantrum and scream about a cuddle and a kiss. Not only would he scream, he would get out of bed and kick, hit and punch his door. We started locking his door with a hook and eye for his safety as he can unlock the front door and leave in the middle of the night. (He would do so as well!)
Anyway, this 'changing his mind over and over' happens ALL THE TIME, EVERY DAY.

He'll say he wants one thing, and change his mind as soon as I agree, then if I agree with that, he'll change his mind again.

Getting him dressed in the morning is a nightmare. He'll want to stay in his PJs and since I'm a stay at home mom, I'll say, fine (as he has no school or daycare) and then he'll change him mind to wanting to get dressed.

It drives me insane.

If I force him to get dressed, he'll kick , scream, wriggle and whatever he can to stop me from dressing him.

I've tried time out.
I've tried spanking him.
I've tried bribing him.
I've tried agreeing with him on everything.
I've tried ignoring him.

I've tried everything.

When I used to lock him in his room when he'd have a tantrum, he would kick his door as I said. One time I left him to kick it and he kicked it so much, he made his toes bleed and didn't even notice.

He's kicked it so much, the piece of wood along the side of the frame (the stop thingy) has come off. The top one is now starting to come off as well.

I admit, he's driven me to the point of slapping him in the face as he just won't stop. This does nothing to affect him. He doesn't even register it. I feel awful for doing it and I feel like I'm a terrible mother.

His older sister has NEVER acted like this. Not even close.

He doesn't listen either. He never registers us saying his name to him, or if he does, he ignores it.

This morning he wanted a banana and I told him no since we were going to have lunch shortly (and for the last month he doesn't eat them, but smoosh them up on the table)
He then started screaming for lunch. I told him it wasn't time for lunch yet, and I had to finishing breastfeeding his 3 month old sister first.
Well he stood in front of my chair going on and on about lunch. "Get luuuunch. Get luuuunch. Get luuuunch. Get luuuunch."
I kept telling him;
"When I finish feeding your sister in 15 minutes, we'll have lunch."
"Get luuuunch"
"15 minutes"
"Get luuunch"
"14 minutes"
"Get luuunch"
"When I finish feeding your sister in 10 minutes, we'll have lunch."
"Get luuunch"
"What did I tell you?"
"Get luuunch"

It just didn't register. He would still go on about having lunch that instant and couldn't comprehend what I was telling him.

I'm seriously questioning whether or not something is wrong with him or me. Maybe he's fine and I'm doing something wrong. I just don't know anymore.

He honestly never listens, ever. It's like talking to a wall.

On the other side of the coin, he is the sweetest, most loving little boy. He is smart as a whip and picks things up so quickly, he has surpassed his older sister (14 months older) in some things like language.

Is this normal? Am I doing something wrong?