I want to know when to use IN and inside. If i have to say look in the refrigerator or look inside it, which one is correct?
When you look in the refrigerator, you are also looking at what is inside the refrigerator. There is no difference in meaning. It is simply that we say "look in the refrigerator".
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.