To my understanding ACE only works on Gambatte as there's hasn't been full console testing to say it works on console. I've heard that people haven't managed to get it on BGB.

As for how it works... I think this website explains it.. http://hogehoge61.web.fc2.com/TAS/LA_ACE.html

Clear, concise explanation website Warr.

:P

Haha yes, I forgot to mention that it's all in Japanese with loads of numbers and boxes.. Also some colours thrown in there :P