Can I claim deduction if renter did not pay rent for a few months?

I am a homeowner and am renting out part of my house to a tenant. My renter did not pay rent for 4 months in 2023 but has paid me for the missing months in 2024. Normally I'd take deductions with home mortgage with this rental situation (Schedule A and Schedule E) but I don't know how my taxes will be affected for 2023 and 2024.

1. How will my taxes in 2023 get affected? What about 2024?
2. Can I take a deduction with my mortgage interest with the missing rent?
3. Due to 4 months of missing rent, will this potentially cause my rent income to be marked as renting below fair market value?
4. Any other advice would be greatly appreciated