Can't send the gift

This might happen if the user has the spectator client installed (I'm not sure).

You should still be able to trade the game to him or send it by e-mail.

if he own it already, u have to do re-roll and tell support to ban that guy who entered a giveaway of game he already owned

Does the person have DOTA 2 in their library? If so reroll

Just wondering, why have you won and received 4 giveaways of Dota? 3 of those should be re-rolled...

This thread was your undoing, friend.