Which class should I take first?
Slow Flow, Gentle Yoga or Restorative are the easiest doors; every card on the Classes page says how warm the room is.
How warm are the rooms?
Rooms run from non-heated, to cool at 76°, warm at 80°, heated at 83°, and hot in the mid-to-high 80s. Every class card says which.
Do I need to be flexible?
No. Flexibility is something a practice gives you, not something it asks of you first.