Giveaway won

you can ask for a re-roll that on GA page, but it is up to the GA creator if they are going to open up the support ticket to do so. Don't use the key for now, and wait to see if the creator responds to your request.

You shouldn't ignore it, you need to ask for a reroll.

Comment on the giveaway that you no longer want the game, and would like a reroll.
Staff will need this before they'll agree to a reroll.
Make sure to leave the giveaway feedback unmarked, or as Not Received.
So long as you don't use the key, and don't mark Received, you won't get into any trouble.

That said, it's a developer giveaway for a F2P game that's being spammed everywhere.
It's unlikely that they'll bother to go through with the reroll, so expect that you'll need to mark Not Received.

Thanks for all comments.

With 10000 keys usually it's going to be alot harder to get a reroll, and you don't know what you enter?

since it's a mass GA you should ask for a reroll, 18k entries and 10k keys give a lot of room for that. shouldn't be a problem.