formal and informal

[bahia]

with whom will you be travelling to london?
who will be travelling with you to london?
who will you be singing with?
who will you be singing with you?
which questions are formal and which are informal?and how do i know?
thanks alot.

[engee30]

With whom will you be travelling to London? formal, I mean putting the preposition in front of whom makes such usage formal
Who will be travelling to London with you? normal, I mean used in formal and informal language
Who will you be singing with? standard, I mean commonly used in everyday speech
Who will you be singing with you? normal
which questions are formal and which are informal?and how do i know?
thanks alot.