Repeat Main Quests after Berna with Boosted ch

Hey guys, i don’t undertand how the boosted characters works. The question is:

If i’m like 600 item level with my main, do i have to do rohandell AGAIN with the alt (or w/e its called lol) to unlock t2 chaos dungeon? Some people say that i have to and other people don’t.

Thanks!

No One :(?