Applying for Canadian Citizenship and Leaving Canada for 3 weeks

Hi People,

Trying to apply for my Father's citizenship (62 y/o)

We're submitting the citizenship at the beginning of February. However, he plans to go back to his homeland for personal reason but will only be there for 3 weeks.

Submitting the Citizenship Application early february and leaving canada around April 15, 2025

Question,

  1. Is he allowed to leave canada while the application has been processed or submitted?
  2. If we received an email about his oath taking and he's still currently not in canada, what are the chances of the application to be denied?
  3. Can we reschedule the oath taking if possible?
  4. Do we have to pay another citizenship fee and reprocess a new application?

FYI, we landed as permanent residenct in Canada on 2015 (i am already a citizen and he's not)

TIA