After from the previous log, I took a look in the EmuVT's debugger and noticed that there are many jumps to a nearby locations and "strange" opcodes that don't make any sense:

Hmm... looks like some of the stores especially at the $412D could make sense, since these stuff often use the registers around that address. And the jumps too. Look at the end with the "F5FE" - looks like a jump to the main startup code?

Wait... I recalled about chatting about those VT-02 OneBus systems at NesDev Discord, and also these NesDev article: https://www.nesdev.org/wiki/NES_2.0_Mapper_256, and another BGC article: http://bootleg.games/BGC_Forum/index.php?topic=2412.0

Something reminded me that there could be swapped bits somewhere in the opcodes. After checking these instructions on a pen and paper, bits 4 and 5 at the opcodes are actually swapped!

After swapping these bits manually in HxD and pasted this modified code back, it runs on the EmuVT now!

These newer Sup 400-in-1 handhelds are having these strange bit-swaps at the addresses, and this one having a bit-swap at its opcodes before the startup happens!