Ivan are the 212 and 412 subs smaller versions of the 812?
They are all tapped horns-so they have that in common.
THe TH412 and TH812 use the same drivers. The TH212 uses a slightly less powerful woofer (2dB power) because the ones in the 412 and 812 won't fit.
The TH412 has a longer horn path than the 212 and the TH812 has a still longer path.
In all of them the drivers are in a kinda "push pull" configuration. This is done to be able to get the drivers physically closer together so they have a closer source of origin.
The overall physical layouts are different. Only the TH212 (of those models) has a selectable physical output location for different uses.locations.