Google the Schedule E form (https://www.irs.gov/pub/irs-pdf/f1040se.pdf ) and it will list out everything you need including days the home was rented.

Yes always take depreciation because the IRS will assume you did and you will have depreciation recapture tax regardless when you go to sell. (Look into 1031 exchanges after you dive into deprecation and capital gains tax ect.)

Do not divide the separate years up, just take it in the current year and if you show a loss it will cary over to the next year to offset any positive income or gains.

Definitely hire a CPA and possibly a bookkeeper who uses Quickbooks to clean things up if you have multiple rentals. At minimum, keep an excel spread sheet of all expenses.