Beta Game Allow or Not Allow

Did you really try?
https://www.steamgifts.com/about/guidelines
Giveaways > Creating > 2nd bullet point.

Generally not alllowed because the key will be revoked in the future (from massive giveaway site)
But that is alowed for devs that want give there games, and there often just can create beta keys, but there add in the description giveaway that is beta keys but the keys will not be revoked.