The bad thing is that the events are inside the core, w/e you want to change you have to recompile. xdem could make them load from datapack, listeners, xml and so on.. ;)
Actually, I have doubts. You didn't saw Trance's engine. Anyway, good luck :)
Bad, so bad. The olympiad check probably is while registering, so well.. You may register and then equip it and voile, you are with S grade.
The check should be zone related with auto unequip.
Switch dsetup/fire/core/engine/nwindow .dll and the error will be gone :P
I don't remember which exactly was for this error. Yday I was switching them, and I didn't noticed which one it was, I guess the engine.dll - but dsetup/fire dll is required to disable GG (update) :D
No idea how h5 multisell works. But well, maybe you added the multisell while the server was online and you didn't reload it? :P
Someone who uses H5 for sure will tell you what's wrong.