Sonic Adventure DX: Director's Cut/cheats

How to get all A ranks
Note: You must have completed the level' with a C Rank before you can get a B Rank, and a B Rank before you get an A Rank.

All of Sonic's levels

 * Rank C: Bet the level
 * Rank B: Beat the level with 50 rings
 * Rank A: Beat the level within the time limit

Tails

 * Rank C: Beat Sonic (or Robotnik)
 * Rank B: Beat Sonic (or Robotnik) with a total of 50 rings
 * Rank A: Beat Sonic (or Robotnik), they are faster this time.