Good timing. I'm here trying to remove yxplayer's trial / 2min time limit. Managed to decompile, edited smali files, recompile, sign. So far so good, worked as expected (re-mapping various functions to different buttons). Now gotta hunt down the code which actually triggers that 2min play limit, and with some luck, maybe the whole validate-the-serial-number routine
PS: was using only APKTool
& Auto-Sign. Will check out the tools in Avabox and see if they will be useful.