Can anyone explain the difference between hence and thus and when should we use one and not the other?
"Hence" means "from here". "Get thee hence!" is old English for "get out of here". "Henceforwards" is "from this time on".
"Thus" means "in this way". In older English, you might say "he opened the door thus", while demonstrating the action.
In logical senses, you can use them in similar contexts. "If x is true, then y is true. X is true. Hence, y is also true." "If x is true, then y is true. I have proved x is true. Thus, I have proved y to be true also."
Think of them as "based on this fact" and "in this way" and you can't go far wrong.