Depreciation for the converted property

[Carlos Ptriawan]

Hi Folks,
Let's say I have a primary that I bought in 2000 and I started renting it out in 2010.
Question:
- is the depreciation calculation is started from 2000 or 2010 ?
- let's say by 2020, I want to change the method of calculating depreciation, meaning If I use the appraisal method, I found the depreciation number is higher rather than using the tax method which I've been using so far. Can I change the method of taking depreciation after so many years? is it allowed? if yes what's the mechanism? 
- when selling, is the IRS only checking schedule E depreciation item only? 
- In scenario where I move back to the house in 2020 live there for 5 years until 2025, and rent it again after 2025, how's the depreciation is calculated in this case ? will it continue from 2020 or a new fresh start ?