When at the Stage Select pop-up displays, press the C-Buttons to rotate and R and Z for zooming.
Keep Black and White Yoshis
If after you beat the game the Black and White Yoshis are still alive, then , when you start a new story, both the Black and White Yoshis will be available.
Unlimited Continues
When you are losing your last life, hit reset and you will be able to restart on the page you died on.