Off the bat, I'll very briefly list off some things to know. Levels are stored in a very similar method as Sonic 1's levels, but the block data in the chunks is stored like Sonic 2. Chunks, blocks, and collision indexes are compressed into the "Star" format, dubbed by drx. Collision is stored identically, albeit arrays are smaller. There's some sort of angles being handled here, but I'm currently unsure where they're handled. Ristar levels will work perfectly in SonLVL if you modify the source code to make Sonic 1 projects use Sonic 2's "ChunkBlocks". Currently, data in the Star format can only be decompressed, as there's no available compression tool. It seems to be similar to Kosinski, in fact replaces where Kosinski should be in these games. It's even set up identically: lea Source, a0 lea Destination, a1 jsr StarDec There's a LOT of game modes, almost all of them are blank. $50 is the Sega screen, $54 is the opening sequence, and $0C is the level mode. I'll showcase a video of a level edit test I've done so far: May list more things off later, but this is a generalization of what I have down so far.
