Makon Soft games do not run properly on emulators (either due to their shabby programming, or some kind of copy protection). Li Cheng sometimes patches up other companies' bootlegs and slightly alters them to resell. Unfortunately Li Cheng only translates Chinese ROMs as that is their country of origin. I think Pokemon Adventure is the only Makon Soft game that has a ROM available that actually is just a fixed version of the original version and not just a Li Cheng hack, but I am pretty sure that the people who dumped that ROM did not dump Mewtwo.
(The one on hhug.me is from the Li Cheng Extravaganza part 4, by Taizou).