Sonic the Hedgehog 2 (16-bit)
The Perfect Bonus first appeared in Sonic the Hedgehog 2 (16-bit) where in order to clear an Act with it, the player must have collected every single Ring in the Act and must not lose them (being attacked by enemies or obstacles etc.). This does not include any Rings earned from Super Ring Monitors or from Rings placed with Debug Mode. Upon clearing the level, the player gains an additional 50,000 points, the equivalent of an extra life.
Sonic the Hedgehog 3 & Knuckles
In Sonic the Hedgehog 3, Sonic & Knuckles and Sonic the Hedgehog 3 & Knuckles, Perfect Bonuses only appear in the games' Special Stages. To obtain a Perfect Bonus, the player must collect every single Ring in the stage (including Rings formed from Spheres), upon which the player is notified that they have gotten a Perfect Bonus. Also, whether they successfully collect the Chaos Emerald/Super Emerald or not, the player will be given a Perfect Bonus category in the score tallying that grants 50,000 points (and an extra life), much like the Perfect Bonus in Sonic the Hedgehog 2.
The Perfect Bonus appears again in Blue Sphere where the conditions of obtaining it remains the same from Sonic the Hedgehog 3 & Knuckles. Instead of getting bonus points or an extra life though, the player skips ten levels instead of one.
In Sonic Generations, the Perfect Bonus functions differently from its previous appearances. In this game, the player receives it whenever they complete an Act without losing a life. Gaining the Perfect Bonus increases the player's Rank by one level after the score finishes tallying. This is the only way for the player to receive an S Rank for the Act as they can only get an A Rank at the highest on their own.
In Sonic Mania, and its expansion Sonic Mania Plus, the Perfect is awarded during the Bonus Stages. It is given under the same conditions as in Sonic the Hedgehog 3 & Knuckles and Blue Sphere (collecting every Ring from the Bonus Stage, including rings that must be transformed by enclosing blue spheres within a box of red spheres). Clearing a bonus stage with a "Perfect" will award a gold Medallion.