Avoid losing lives
To prevent a loss of a loss of a life, press Start when you have one heart remaining, and select "Retry". You will go back to the door you went through. This is good for health.

EX 3 option
Successfully complete the game after collecting all the gems to unlock the EX 3 option.

EX 2 option
Successfully complete the normal and bonus levels to unlock the EX 2 option.

EX 1 option
Defeat the final Boss to unlock the EX 1 option.

More lives
Keep entering the first Hoverboard stage. Get the first life, then keep going until you get to the hill with a sign. Jump to get the second life. Then, head for the finish line, and jump for the last life.