Timing starts on reset (or power on), so after the countdown, reset your game. Be sure to clear File A on the file select screen beforehand so you can start without moving the cursor.
Streaming is generally not required, however for larger races it may be enforced. All officially released versions of the game are legal for racing, if racing on emulator please use a leaderboard legal emulator (see the emu setup guide).
Complete the game while collecting every star. No restrictions.
Complete the game as fast as possible without circumventing any star door requirements. All forms of BLJ and Mips clip are banned.
Complete the game as fast as possible using Mips clipping to skip the 30 star door. Any form of BLJ (or technique other than Mips clipping) to pass the 30 star door is not allowed. Other instances of BLJ are allowed, including LBLJ.
Complete the game as fast as possible. Skipping Dire Dire Docks is not allowed.
Complete the game as fast as possible. No restrictions.
Consult the category extensions for the specific rules for each meme category. Generally, meme categories follow the same basic restrictions as 16 star (e.g. SBLJ is banned).