I feel obligated to mention the "hacking" aspect. Using GD Bot Mobile to auto-complete levels for stars and cubes is, frankly, cheating. It ruins the integrity of the leaderboards. However, the developers have positioned it largely as a practice tool, and for that, it is invaluable. I strongly recommend using this tool to learn levels, not to steal crests. The satisfaction of finally beating a level legit after practicing with the bot is infinitely better than just letting a script run its course.
Apple restricts modding heavily. You will need a computer (Windows or Mac). gd bot mobile
A popular mod available through Geode. It features a simple macro recording and playback system , frame stepping, and speedhack. I feel obligated to mention the "hacking" aspect