These are good questions!

1. how will i know whether i love myself?
Are you comfortable being alone/like spending time with yourself? Do you engage in self destructive behaviors (e.g. binge eating, drugs/alcohol, inappropriate sexual relationships, cutting, etc)? What's your self talk like (e.g. mean, putting yourself down or positive/encouraging)? Maybe answering those questions for yourself will help you assess how much you do or don't love yourself.

2. how does love feel like? whether we love others
It feels good! and when you really love someone, more than anything you want them to be happy and to have good things in life, whether or not that includes you.

3. my mom says that i dont love myself hence i have poor social adjustments and depression and behave weird.
Depression is a clinical diagnosis made by a trained professional, with treatments available. If you are concerned that's true, you should see your regular doctor and talk to him/her about it. If needed, they'll refer you and if not, maybe that'll be reassuring. Social skills are just that, skills. Skills are learned. Yes, it comes more naturally to some people, but all people become more socially adept over time as they have more experiences. There are books available that teach people how to interact with others, some are general, like the classic How to Win Friends and Influence People, and some are specific (e.g. cross cultural). "Weird" is a subjective view. Take it with a grain of salt.