How long does or take to recover from knee replacement then scar tissue removal surgery?

Few weeks. It depend how much scar tissue were taken out, it take about 4 -12 weeks.
It varies. It also depends on what you mean by recover. If you mean up walking on your own without assistance and no walker or cane probably 6-8 weeks. Depending how badly you scar you may not need scar revision but recover from that should be much shorter.