>How to enter test mode, press L3+R3?
Yes.
I don't know how to post replies on this board :)
BG3T will not be able to go into test mode unless passing patches for rack and handle errors are received.
Currently, only the English version of BG3 (v2.01A) has a handle patch.
When the TAITO logo appears, the test button will be enabled.
The English version of BG3 was recently made compatible with M.A.M.E. Emu.
Since the compression option for CHD is set to CD, it is necessary to recreate it with an HDD.