How do আপনি know if আপনি like someone অথবা if someone likes you?

If আপনি like him then when you're near him আপনি might feel tingly, say stupid things অথবা speak in a different voice then আপনি usually do. If he likes আপনি then he should be doing the things listed above.

No one can answer that প্রশ্ন but you.
Each person is different.
If আপনি don't know if আপনি like him and we are on the internet how am I supposed to know never seeing অথবা being around either of you?

Have আপনি ever liked someone?

I could answer like some others and say, "Girl! Do আপনি find yourself thinking about him at random/odd times? Do আপনি ever have him pop into your dreams? Do feel অথবা act different around him... like not yourself, uncomfortable অথবা all প্রজাপতি in your stomach?" but yeah it takes a little time to know. Give yourself a chance to find out. Symptoms vary. Some people are আরো cool and collected but maybe inwardly they just question, like আপনি are... give yourself আরো time around this person আরো and THEN you'll really begin to tell & answer your own question. :)

Liking someone is আরো than just a feeling and feelings are deceptive