Rings are tracked in Time Attack mode, so there's no time warping involved. (Zeupar, please add a rule for this, since no other admin will.) If a record seems impossible, it's because people are glitching through the walls to get rings normally only accessed in other time periods.
Such as Metallic Base Act 2 where you have to go to the future to beat the level, there is no other way to beat act 2 in past or present.
Wrong. If you have the Sega CD version of the game, the level cannot be fully beaten in the past due to a diagonal spring being a few pixels too high, causing you to smack the ceiling early, fall too soon, and not reach the ledge that leads to the rest of the level, but all other time periods are fine (else how would Time Attack mode work?). This is fixed in all subsequent releases, so every other version allows you to beat the level in every time period. There isn't any release of the game where you are required to warp to the future to beat the level.