It enables you to run raw(unconverted) spectrum games/programs from the sd card?

Yes. The hardware look for Spectrum events (write to attribute area, read/write FEh port), generate NMI, and the emulation routine in the ROM do the emulation on the fly. LOAD/SAVE also modified for using EXOS devices instead Spectrum tape. It is possible load TAP files.

You can try it in ep128emu, because it is also emulated
Programs can be loaded which are using the standard LOAD ROM routine. If the program using special loader then need to find cracked version in .TAP format
Palette converted, and beeper sound also emulated. But if the programs hardly use the beeper it will be very slow and crazy

The original official ROM have a many bugs, especially with IM2 mode. I think this is about 20-30% compatibility.
With my enhanced ROM I think about 60-70%, sometimes need a turbo machine for a right speed
Need to test lot of programs

Yes, but not all. Compatibility is on 70%level. BASIC programs runs correct.

Bring here the name of games made with that engines. Then we can test them on the hardware emulator.

If they are which changes attribute by pixel line then no, because attribute conversion is done on emulator when an attribute is written, and it slows down the game, and picture timing is lost.

Yeah, the ones like "Snake escape", "Alter ego"... So as I thought