They will only swap the ONT if there's some kind of damage to the ONT itself, but hypothetically speaking if the ONT and fibre is fine, then there's no need to swap the ONT. Changing of services on MFN is done logically.
Depends on the fibre provider, with this line being on Openserve's infrastructure. This shouldn't take too long as your B number is already set to go live by Openserve's systems. We need to give this up to 24 - 48 hours.