Just apply
this patch to the MKDS ROM, then copy it on the G6 Lite with the U-Disk Manager, as usual. That's it. Go play online and the "hidden" tracks should be there.
Optionnally, you can also hex edit the patched ROM to select the tracks you want in the list (it contains only a limited number of tracks, so it's impossible to have them all at the same time).
The detailed procedure is explained
here. It's for M3, but it works for G6 Lite too.
There's also a method using a loader which launches the original MKDS card, but it didn't work with me.