so a won another game yay me but it was a beta key :(

First of all, you should check if it's one of those Beta-but-you-get-the-full-game-when-it-ends keys. I don't know the details on how to do that, so I'll let someone else explain it more in depth... ^_^'

If it is a Beta-only key, then you should ask the giveaway creator if there was some kind of misunderstanding.

If they don't provide a proper key and you didn't get the game, then you mark it as Not Received.

Some keys are activated as beta because they were generated at that stage of development, but are fully working keys. Check if you can have full access to the game.

Giveaway creator has a week to deliver, so for now, tell him/her that key is not what it was supposed to be, and give them time.
But in the worst case scenario look at what guidelines, giveaways section forbid:

Beta keys which do not provide unrestricted access to the full game in the future, guest passes, demos, and coupons cannot be given away.

Which game was it? Insurgency?

Because that game (https://steamdb.info/app/222880/subs/) is included in the Beta key (https://steamdb.info/sub/30555/), so yeah, you will keep the full game.

Unfortunately there is no easy way to know what it means when you activate a key and it is labeled as a beta key. I think it's up to the dev to decide what to label the keys and many devs label them as beta keys if you purchase the game in early access, but you get to keep the game forever because it was purchased. Some devs give actual beta keys to test the game, but have no intention of taking the game away after the beta period. Then there are real beta keys that are only good for a certain time and those are not allowed to be given away here.

I would just ask the giveaway creator how the key was obtained and make sure it is a permanent key before you mark it as received.

First of all contact giveaway maker and tell them about your trouble. Maybe they will provide another key or give you some proof that this beta key will grant unlimited access for the game.
If giveaway creator is not communicative - well, then I guess you have to mark as not received.
You need first step in case if support decide to check this case (for example, if giveaway creator files a ticket to receive positive feedback). Also, it's more polite to try to resolve it peacefully first.

it's fine it's the full game :)