Hi @Henry Ng Tsz Kiu,
So is the A# a signal of tonicization or modulation? I'm a bit confused as in your first answer you said that "the A# the music is modulating to B major, the dominant of the tonic key of the tonic E major", while in your second answer you said that "The A# appearence is the signal of a tonicization, that is, making B major the temporary tonic."
Thanks, Pano