No and no! Please wear what you're comfortable wearing. If you've ever wanted to wear Indian clothes this is the best time to. It is not cultural appropriation if you come in a sari to an Indian wedding that you were invited to.
No it is not. If you wish to gift the couple, please only do so at the Wedding/Reception, similarly to Western/American tradition.
There will be food provided at all events! And the cuisine will be primarily Indian. If you've never had Indian food, don't worry it won't be too spicy. If you have allergies (especially to peanuts,egg/dairy, or cinnamon) please check the labels and ask a server. Indian food likes to sneak peanuts in things you'd never guess!
Usually people do, and the majority probably will, but it is definitely up to the individual if they want to. If you are coming from out town and need somewhere to change please let someone know. There are plenty of place to do so!