Okay, I'm back and can be more useful now.
Let's start from the top with the first set of code, and work through issues, moving down to the other codes when the first issues have been dealt with.
The A code seems to be doing its job. The B code isn't removing that background from button A, so that's the first thing to investigate.
Do you remember how "active" is set and removed by play/pause, and that "activated" is permanently set when something has been clicked? The B code is currently not removing "active" from the other buttons, and it should.
The showPlayButton() function is where that occurs. It looks like you removed that line from the B code. You need to put that line back. You'll find the appropriate line in the function of the same name in the A code.