Can a indian tourist buy an iphone5c from US?

If iim an indian tourist and i have to buy an iphone 5c from US then there's preinstalled at&t sim. Or tmobile sim in.it… Please let me know if i can.buy from there and for buyin that cell any papers are required for buyin that phone where there's a simcard preinstalled… Please help…

If you pay full price (not contract price) then yes you can.

Yes, you can buy it, off contract, but just don't buy more than 1 for yourself, or else you might have to pay the custom duties at the airport,
The custom department accepts one phone purchased from foreign countries for self use, but more than 1 as an intention to resell it. So they will charge you custom duties for the phones.

If you have another person coming with you, then you may buy more than one.

No you can't, unless you were buying it unlocked, with no SIM involved