Shouldn't "тобі вже" be also accepted?
Why is it Тобі or Вам instead of Ти or Ви?
Well, this type of structure uses Dative, so pronouns just conform.
I was reading elsewhere that вже follows vowels, and уже follows consonants - why is the answer "вам вже" instead of "вам уже"?
Just because currently this course is kind of inconsistent in following у/в rules :)
Good to know :) Дякую!
Why Bam ?? Why not Bac ?
Because that's how Ukrainian works?... I don't know how to answer your question better than that. "Вас" is a genitive, and "to be X years old" requires an accusative, which for plural "you" is "вам".