OK, I just figured out conditional moves, but I had to completely log out and back in to get to the new version. Is there a simpler way to move between the two versions?
Old v. New Chess.com and conditional moves

The conditional moves in v3 can be found when it your opponent's move and the button looks like a forking arrow; second button.
To get back to v3, there is a link at the bottom of most pages that says Try the new Chess.com that links to www.chess.com/switch
In v3, there is a menu item to switch back.
I just clicked some button to get into the old version of chess.com to try to make a conditional move because the new version would not accept a conditional move and now the old version won't accept the conditional move and I cannot see how to get back to the new version. Please help. How do I 1. make a conditional move in the new version of chess.com, and 2. travel back and forth between the new and the old version of chess.com.