umm just trying to decypher your diagram it appears to show the 2 positive terminals connected to the lamp and the 2 negative teminals connected together.
In this case the lamp WONT glow as there can be no current flow
your actual subject question doesn't have anything to do with the
circuit diag you have posted and the question you asked about current flow
the 2 questions are not related :)
Yes, because there is a potential difference then.
Ground can be any voltage you like as long as you state all other voltages relative to ground. So you could call ground 100V and state all the other voltages relative to this if you wanted... there just isn't much point in doing so.
because i tested this thing with a software livewire 1.1 . the bulb glows if one battery provides 15 v and other 5v. And as there is a difference of 10 volts.