1) For my property placed in service from Nov 2020, can I amend my 2020 and 2021 returns (from 27.5 to 30 years life).
No. Read what is says in IRS Pub 946, of which I highlighted the applicable part in red above.
2). Now the bigger problem - for my property placed in service in 2006 - understand that I will need to seek professional help with preparing F-3115. I don’t live in the US. The expats deadline to mail the 2022 return is on June 15.
Don't know what to tell you, other than it's probably to late to file any extension. I don't know if that's the case for an expat or not though. Since you have to file the 3115 anyway, you deal with both properties on a single 3115. Instructions for that form are at https://www.irs.gov/pub/irs-pdf/i3115.pdf. While you're welcome to give it a try, all I can really offer is best of luck. You may be able to find help or a reference at the local U.S. Embassy or satellite location in your area if that's closer.
