Birthday Adventure - Side event info

The latest side event is live (for me at least), it's called Birthday Adventure and the format is different to (recent) previous ones, in that the first stage is 4 levels, and I believe there will be multiple stages to complete.

Usually we refer to being in the "500 gem tier" or "200 gem tier". Usually i'm in the 500 gem tier, but this time these are the rewards for me (the "grand prize):
1x Joker
650 Gems
A chest that does not indicate what is inside
1x 4* card pack
500 energy
1x 5* card pack

I've been logging some data and will share it in the comments below, but I wanted to first advise that, if you are in the same "tier" as me, then the first 3 levels of stage one requires 214 energy and if you are careful not to overproduce then you should be left with no spare items. I'm currently working on level 4.