Deductions & credits

Thank you!  I read the link.  The survey on the website however doesn't seem, relevant, right?  

My understanding: 

1. If I bought the system in the year 2014 for say $20k and got $5k back from the Fed and $1k from State, then I cannot initiate depreciation with $20k as starting point but I should use $14k as a starting point (20-5-1).  Right? 

2. If the value of the system in the year 2022 was professionally computed to be say $25k (inflation etc), still I should stick with $14k as the starting point, right? 

3. Even if the system was greater than 7 years old, since it was used for residential purposes, when I turn the home into a rental business, I can initiate depreciation and depreciate for 5 years.  Right? 

4. The depreciation method I should use is called MACRS, right?

Please include the same numbering your response so I (and the future readers) can use the info best.  

Thanks!