I think you are being way over ambitious for a beginner.
The Arduino is not well suited to doing those things you want.
For the moment forget about control with fancy devices, you have your hands full just getting your audio to do what you want.
To get something to play backwards you have to load it all into memory and put the samples to a D/A in the reverse order. The arduino has 2K of memory, not enough for a quarter of a second of audio.
So to do this you need a lot of memory. You can't use MP3 because the processor is not fast enough to decode it.
A 180 second audio file at a sample rate of 10KHz will take 3.6 M of memory at two bytes per sample.
Your only hope is to get a Yun and hope that the dark side of Linux offers something.