You have made multiple posts so it may suit you to have a sit down with a local tax pro to get all your questions answered.
But if I understand this question you are trying to figure out how to not pay cap gains on the rental side ... you can't since you cannot have both sides as a personal residence. Even if you let the rental side go dormant for 2 years you will still owe the cap gains and must recapture depreciation as ordinary income. This is the same if you moved into the other side and let your side go dormant. There is no way around this unless you can get the property titled into 2 individual properties and sold one now and one later ... but again even if you did you still have to recapture the depreciation.
Now if you have not been properly depreciating the property as required RUN RUN RUN to a local tax pro to get the mess fixed when you file the 2021 return. The form 3115 is not a DIY project.
