These achievements will all unlock along the way to completing every level of the four level packs in the game, which are Insane Hills, Stadium Stunts, Extreme Skies, and Desert Paradise. Completing a level only requires that you make it to the finish line. The collection of the gold stars is not required, but it is recommended for two of the game's other achievements. To save time, you should attempt to gain a Gold rank on each level before proceeding (this is for the first two level packs only), unless you get stuck.
See "Superstar" for more information about collecting stars.