So after I replaced all the sewer lines under the basement floor to the property line I had one installed $500, (had to get a permit & use a lic. plumber).Then when the city was replacing sewer lines in the street several of our neighbors homes suffered basement flooding with backed-up sewerage.

Three years ago we bought our dream home it was a modern farmhouse on a little over an acre of land in the country.  

These will need replacing now or soon, and this typically costs $8k - $10k I suggest having them camera'ed, here is who we use for that"A prospective buyer should NOT be left hanging after the inspection to make the decision on what is important and what isn't.

We got it rent ready (new carpet, paint, replaced the last of the white appliances with stainless, LVP downstairs...). 

Exceptions were made for owner moving in, owners family moving in, significant remodel of the unit that requires it to be vacant during the work (replacing kitchens or bathrooms, a paint job doesn’t qualify).  

However, one of the benefits of a modern crawlspace is that the sewer lines are above ground, clearly visible and can be inspected for flaws without a scope.

Legally speaking, do I need to replace the fridge with one of the exact size? 

Bathroom vanity (3) need to be replaced.

Restuccoed the house, replaced castiron with pvc, upgraded bathrooms.

I would rescind the offer to have the daughter replace herself on the lease and instead suggest you'll just allow them to end the lease early - but they both have to go or they both stay on the lease.