Stratamax - When you have only one move remaining, you can make 2 matches very quickly. This will cause the moves remaining to go negative, and it won't kill you. (Side note: This is probably the worst way to program a move limit. There's like, 3 easy ways to fix this)

Avalanche - By performing a technique known as Gemwipe, you can basically survive forever. You can learn how about this here - https://bejeweled.fandom.com/wiki/Gemwipe In speedruns, it's best to wait until the board is close to being full before actually using this technique, that way you have more possible matches. That being said, using it early on can be helpful for creating special gems.

The trick in Stratamax also works in Alchemy (2+)!