For the music, there 2 different background music, and in the main menu, the main menu music should be the only one playing. Does adjusting the volume help?
Having Play bring you to a screen with a house with “It is 2084.” is supposed to happen. Is the Continue button (defaulted to Tab) working for you?
I don't have FireFox or Vivaldi, so I'll download those and see if I can replicate the problems after the voting period.