What happens if I use Area Zero Underdepths to replace Sky Field, or vice versa? Does either player need to discard Pokemon because the Sky Field/Area Zero Underdepths stadium left play, or is the transition instantaneous?
As long as you meet the required criteria of the new stadium you would not have to discard any Benched Pokemon since one stadium's effect is replacing the other simultaneously.
Source: TPCi Rules Team (2024-09-26)
Say Sky Field is in play and I have 8 Benched Pokemon, then I use Marshadow's "Resetting Hole" Ability. Do I discard Marshadow first and then discard down to 5 Benched Pokemon for the removal of Sky Field, or do I discard down to 5 Benched Pokemon first and then discard Marshadow?
The player who owns Marshadow can choose the order of discarding Benched Pokemon, either before or after the removal of Sky Field.
Source: TPCi Rules Team (2020-02-06)
Say the "Sky Field" stadium is in play and I have 8 Pokemon on my Bench. My opponent uses Salamence's "Shatter" attack to KO my Active Pokemon and discard the stadium. Do I promote one of my Benched Pokemon first, or do I reduce my bench size to 5 Pokemon before promoting?
When the Sky Field stadium is discarded during the attack, the bench size is reduced immediately before going any farther. So after promoting your new Active Pokemon there will be 4 Pokemon on your Bench.
Source: TPCi Rules Team (2015-04-30)