They're not incremental.

The RetorN1 is just a renamed version of the Yobo FC Game Console. It's also sold by RetroBit under the name Retro Entertainment System. It's simply a NES NOAC.

The RetorN2 was recently released> it's essentially a RetorN3 without the Genesis. SNES and NES only, and like RetroBit's RetroDuo it only uses SNES controllers for both SNES and NES.

The RetorN3 has several revisions. No matter how you slice it the thing has problems.

The RetorN4 will likely be another revision of the RetorN3 that *hopefully* fixes problems and also adds new stuff.