Alright, here's the lowdown on Sonic Rivals 2.
Eight Playable Characters:
-Sonic (Special: speed boost)
-Shadow (Special: slows down opponent)
-Knuckles (Special: fiery ring surrounds him)
-Silver (Special: screws up opponent's button arrangement)
-Tails (Special: flying)
-Espio (Special: invisibility)
-Rouge (Special: flying projectiles)
-Metal Sonic (uses opponent's special)
6 Zones (Act 1: Race; Act 2: Battle; Act 3: Race; Act 4: Boss)
-Blue Coast Zone
-Sunset Forest Zone
-Neon Palace Zone
-Frontier Canyon Zone
-Mystic Haunt Zone
-Chaotic Inferno Zone
6 Battle Modes
-Knock-Out
-Tag
-Ring Battle
-King of the Hill
-Capture the Chao
-Laps Race
4 Single Player Modes (Story, Single Event, Cup Circuit, and Free Play)
150 unlockable cards (150 specific tasks, instead of generalized challenges)
Wireless Multiplayer (and "game sharing" options)
Some of the largest mechanical differences between Rivals 2 compared to the first:
-Specials are separate from power-ups. They're charged by collecting rings and killing enemies, instead. Also, the specials' lives can be extended by rapidly pressing the square button (except Rouge's; the projectiles launch by pressing square)
-You can't see a power-up before grabbing it. This makes key items like the magnet ring much harder to obtain.
-Better movement mechanics (Trust me. One specific example: you no longer randomly fall off sideways loops when switching between rolling and running in these areas).
-Power-ups are significantly less offensive/slower in this version. No more getting randomly hit by a power-up at the most inconvenient of times when going fast, although they're still good to help stop the other person from catching up. There's also several new power-ups.
-The addition of a series of new obstacles
On the competition side of things:
-All standard races track scores, rings, and times.
-In free play, there's no power-ups, no opponent, and no score; there's just ring collecting, chao collecting (once chao are collected, they're gone), and racing through the level. Note: since there's still enemies and rings in the levels, specials can still be used.
-Boss scores and rings are potentially infinite, like before, so that leaves just times competition-wise.
-Story Mode uses a mixture of race, free play, battle, and mission levels (aka partial race). In other words, usable stages fall under single event and free play.
-There's an unlockable circuit cup for each character. These are nothing more than several of the acts put together (a.k.a. Single Event matches)
-All the battle modes are broke into three different settings. Tag, Knock-Out, and King of the Hill have very little competition potential. Ring Battle (rings), Capture the Chao (time), and Laps Race (rings, score, time; it's just a portion of a level from the zone) would be trackable, although their relevance is questionable.
Character categories:
I'd say to make them "Sonic", "Tails", and "Other". Sonic still always has the upper hand in pure forward speed (more noticeable than before due to the ring-based special charging system, allowing for more use), Tails can skip major obstacles and jump to new paths with his flying ability, and all other characters only effect the rival's movement in some way or another. This only applies to races and free-play, bosses are unaffected by character differences.
As for playing as Metal Sonic, he would either be treated as the character he's copying, or to avoid confusion, just say not to play as Metal Sonic for competition.
Specific Ruling Changes:
It's now all but impossible to discern power-up attacks from physical attacks, so the attack cap for score runs will probably need to apply to the combined number. I'd say eight is reasonable, since they have a challenge card for that many attacks.
Current divisions I'd recommend:
Times/Scores/Rings:
(These should be further broken down into "Race" and "Free Play" subcategories, but I'm leaving it like this to avoid clutter. Scores wouldn't apply for the "Free Play" subcategory.)
BC Zone Act 1 Sonic
BC Zone Act 1 Tails
BC Zone Act 1 Other
BC Zone Act 3 Sonic
BC Zone Act 3 Tails
BC Zone Act 3 Other
SF Zone Act 1 Sonic
SF Zone Act 1 Tails
SF Zone Act 1 Other
SF Zone Act 3 Sonic
SF Zone Act 3 Tails
SF Zone Act 3 Other
NP Zone Act 1 Sonic
NP Zone Act 1 Tails
NP Zone Act 1 Other
NP Zone Act 3 Sonic
NP Zone Act 3 Tails
NP Zone Act 3 Other
FC Zone Act 1 Sonic
FC Zone Act 1 Tails
FC Zone Act 1 Other
FC Zone Act 3 Sonic
FC Zone Act 3 Tails
FC Zone Act 3 Other
MH Zone Act 1 Sonic
MH Zone Act 1 Tails
MH Zone Act 1 Other
MH Zone Act 3 Sonic
MH Zone Act 3 Tails
MH Zone Act 3 Other
CI Zone Act 1 Sonic
CI Zone Act 1 Tails
CI Zone Act 1 Other
CI Zone Act 3 Sonic
CI Zone Act 3 Tails
CI Zone Act 3 Other
Bosses:
BC Zone
SF Zone
NP Zone
FC Zone
MH Zone
CI Zone