You wouldn’t able to come back after 90 days and take part in a contest with no prior posts within 90 days. So you’d need to make a post and wait for the next contest. 

So if for example I disappeared to the wind blowing lands of Siberia and haven't been active for 90 days, is it retroactive? I need 90 days of activity + 5 non-contest posts to be eligible again?  

Zeus vs hades 250-   1191.10x Spellwin casino 

I am a VIP player at Red Star Casino but have never received any special rewards from this casino. I don't know what the advantage of being  VIP at this casino is.

Personally, I use the no deposit bonuses I receive from the casinos where I play and make deposits. If I win, I won't have any problems withdrawing my winnings. However, I don't like no deposit sign-up bonuses, generally, the bonus wagering requirements are very high and the maximum cashout is not very generous.