basement bathroom remodeling

I am remodeling my basement bathroom and I cut up the concrete floor so that I can move drains for shower, toilet and sink. My two questions are ; Can I use a flexible fernco coupling to adapt 4″CI to 4″PVC and have no worry about backfilling and repouring concrete.
I was installing pvc and a couple of times I messed up , getting in head of myself by priming and cementing a couple of joints but realizing that I had wrong joints together so I pulled them apart while the cement was still wet, wiped off excess and put aside then when I was ready to use them I re-primered and cemented, is this ok to do or have any of you guys done this and had no problem with a joint leaking? I was joining 2″pvc pipe to 22 degree fitting using Oatey purple primer and Oatey Heavy Duty cement. Please help me put to rest my worring mind.