Computer Deduction and Usage Question

I purchased a computer on 11/26/2021 with a credit card, starting using it in my business on 12/01/2021, and paid for it on 1/11/2022.

 

Being that it was purchased and used in 2021, but not paid for until 2022, can I claim it as an expense in 2021?

 

Also, I purchased another computer in 2019, which I think I claimed as an expense on my 2019 taxes. I'm pretty sure I took the single year deduction instead of depreciating it over time. I have a copy of my tax return, but can't seem to find this information. Where is it located?

 

The computer purchased in 2019 would have been listed as 50/50 business and personal use. Now that I have two computers, I will be using the one from 2019 mostly for personal use and the one from 2021 mostly for business use.

 

Is there anything I need to do regarding the 2019 computer now that the usage has changed? And if I end up selling it and then the usage on the 2021 computer changes to 50/50 business and personal, then I would need to note that on my 2022 taxes?