Rookie here. Help me with beta please?

Hi lads,

Basically the title.

Yesterday i saw the game on YT, instantly felt in love with it but i am confused about beta.

If i buy the game i instantly get acces to beta or its already full?

If i dont buy it i will still have acces to the beta or is is more like a luck thing - like having the luck to be among those chosen to play this for free - with Steam request?

Dont get me wrong i am gonna buy and play the game like a madman i am just curious if i must buy the game to acces beta or i can get acces free anyway.