Failed to take rental depreciation in 2020 and 2021. Can I amend them now?

Started renting out our 1st home in 2020, when we moved out to a new home. Failed to take depreciation in 2020 and again 2021. Sold that rental in early 2022 (renters moved out in Feb and sale closed in March) -- made me realize that I had failed to take depreciation, when trying to do 2022 taxes. 

 

1. Can I amend the 2020, and 2021 taxes now?

2. If yes, can I mail both of them at the same time (in separate packages)? Or should I do something like mail 2020 first, and may be 2021 a week later?

3. Am getting mixed responses on whether I should file 3115 this year. Should I? 

4. As 3115 is complicated - I would be using TT only if I dont have to include it. In that case, should I go ahead and use the depreciation numbers from the amended returns? 

5. Can I still efile 2022 returns with the depreciation taken now? Or wait for amended returns to be processed by IRS (may be file an extension for this year - no tax due as far as i can tell). 

 

TIA