@Carl @AmeliesUncle
Thank you so much! You are totally right. Found this is explained in Sch E instruction and Pub 527. That "any days you used the unit as your main home ... do not count as personal use".
In rented out on 4/1/2017 and entered 90 days for personal use. After corrected it to 0 days, found two changes happened.
1. The whole depreciation now counted into expense, and the excess amount are treated as suspended loss and reported in Form 8582.
2. Whole amount of mortgage interest and property tax and other expenses are not split between Sch A and Sch E. This is same as my hand calculation using Pub 517 worksheet 5-1.
Now I connected all dots. Thank you all very much!
Last, can I mail 2017 and 2018 1040-X at the same time (in different envelopes)? Here's the IRS information. https://www.irs.gov/newsroom/amending-your-tax-return-ten-tips, anything else worth notice?
