2.1:Perfect bonus

The perfect bonus is an additional score bonus that rewards players with 50,000 points if they collect all rings on the map, including Super Ring Monitors, and finish the level without losing any of them. While the perfect bonus may be useful in a regular playthrough because it gives the player an automatic extra life from the score bonus (plus additional extra lives after collecting the 100th and 200th ring), it is especially crucial when trying for a high score in Record Attack. In most of SRB2's stages, the combined score from the perfect bonus and the ring bonus (100 points for every ring that is brought to the finish) is enough to beat the score emblem requirement.

Whether or not a perfect bonus is awarded in a level is set by the BonusType parameter in the level header. The perfect bonus is awarded if the parameter is set to Normal (for regular levels) or ERZ3 (for regular levels with a boss at the end). It is not awarded if the parameter is set to Boss (for boss levels, where getting a perfect bonus would usually be trivially easy) or None (no bonuses at all).

Perfect bonus in SRB2's levels

An extra emblem is awarded for getting a perfect bonus in any non-secret stage, excluding boss levels where the perfect bonus is disabled, but including Egg Rock Zone Act 3, Aerial Garden Zone and Azure Temple Zone. The ring requirements for a perfect bonus on each stage are as follows:

Level	Rings	Info
Greenflower Zone Act 1	285	This is the easiest stage to get a perfect bonus in, since the ring requirement is low and there are few hidden rings. All three characters can get the perfect bonus.
Greenflower Zone Act 2	339	All three characters can get the perfect bonus, but it requires difficult Crawla bouncing as Sonic. For Tails and Knuckles the perfect bonus is fairly easy to get.
Techno Hill Zone Act 1	597	Knuckles is forced onto a different path in parts of this stage, but he can backtrack through the rest of the stage to get the perfect bonus. Likewise, Tails can backtrack through Knuckles' path. Sonic cannot get the perfect bonus.
Techno Hill Zone Act 2	737	Many of the slime pools in this stage contains hidden ring monitors.
Deep Sea Zone Act 1	762	Knuckles is required because there are rings on his route that the other characters cannot access. Additionally, only Knuckles can flood the final room, which reveals additional rings.
Deep Sea Zone Act 2	576	Knuckles is required because there are rings in a secret passage that the other characters cannot access. In the middle of the stage is an underwater waterslide that forms a one-way passage; there are 335 rings before the waterslide and five rings on it. You have only one attempt to collect these five rings, since you cannot re-enter the waterslide. The block maze in this level contains many hidden rings.
Castle Eggman Zone Act 1	497	Sonic cannot get the perfect bonus because there are rings on Knuckles' path, which Sonic cannot access. Tails is recommended since Knuckles' path is much easier as him.
Castle Eggman Zone Act 2	1247	Knuckles is required because there are rings in a secret passage that the other characters cannot access.
Arid Canyon Zone Act 1	705	Due to this stage's open nature, there are many rings hidden in places that are easy to overlook.
Red Volcano Zone Act 1	431	This stage contains a secret area that contains rings and thus must be entered. Apart from that, there are few hidden rings in this stage.
Egg Rock Zone Act 1	620	An Attraction Shield is required for some of the rings in this stage, so make sure to always carry one and don't lose it. There are rings on all three routes of the character-specific split on the left path. The best choice here is Tails, since he can backtrack through Knuckles' path and use the Super Sneakers right behind the point of the split to get through Sonic's crusher gauntlet. The zoom tube that leads to the outdoor room at the end of the left path is one-way. Since the left path is shorter, it is recommended that you first take the left path up until the zoom tube, then backtrack and take the right path, and finally enter the outdoor room from the exit to get the remaining rings.
Egg Rock Zone Act 2	712	Near the end sign is a corridor that leads back to the beginning of the stage, allowing you to go through both paths without backtracking.
Egg Rock Zone Act 3	134	After the drop near the beginning, there is an Attraction Shield hidden behind the first pillar next to the rightmost wall. This makes it much easier to collect all rings and also provides protection during the boss fight. After finishing the race, the timer disappears, allowing you to backtrack through the stage and collect any remaining rings.
Pipe Towers Zone	422	This level has three pipes that act as one-way passages. At the transitions, you should have 163, 248 and 313 rings, respectively.
Aerial Garden Zone	1921	This stage is extremely large and has many hidden areas that contains additional rings, but there are no one-way passages and few hazards besides death pits, so the stage is fairly convenient to explore as Tails.
Azure Temple Zone	906	Knuckles is required for this stage because there are rings on his path. Multiple routes cannot be backtracked and therefore must be done in order. At the last path split, the puzzle route must be completed before the current route or it will become impossible to backtrack. The Armageddon Shield secret contains twenty rings and is thus necessary as well. You can move many of the gargoyles to disarm them for backtracking purposes.