Yes they will. Just take the receipt and tell them that you didn't like it and they'll give you your money back. If you happen to lose the receipt though, it'll have to be put on a gift card if it's over $10 in value. You can basically return anything at walmart except blood testers and opened cd's/dvds.
If you have the receipt, yes Walmart will refund your money if you purchased the cologne less than 90 days ago. Since you do have your receipt - they will refund the purchase price to your original mode of payment be it cash, credit or debit card.
Probably, and if no they'll probably give you store credit for whatever the cologne is worth. Which means you'll be able to use that credit to by other things, whatever they may be, from Wal-Mart.
Put it back in the box and try and make it look unused. It's worth a try.
try google it also