A:AnswerIt's not a button, just a designation letting you know that is the left side. The piece on the other side has an R on it designating right side.
A:AnswerThe short answer is yes.
The long answer: It may be worth looking into. Around Feb. of this year, people en masse were on the Apple Support Community pages complaining that bluetooth devices were either poorly connecting or not connecting at all. I would assume that an expensive item such as this would have been addressed already via updates but I'd look into it further. It's the reason why I went with Samsung.
A:AnswerI find difficulty in hearing the bass very well but that's because it wont stay flush in my ears well either. Once I "jam" them in, I hear a decent enough bass. Usually turn it down via equalizer as it seems too much for me.