pvc fittings

The pvc pipe for our shower drain is too high for the Kerdi floor/drain combination we are trying to install. Anyone have any recommendations on how to remove and replace this pipe with a shorter one? Or any tools or devices to cut down the existing pipe. It’s in the second floor with no access...

Could anyone help me with the best solution to fix this PVC fitting on our shower mixer? I’m guessing I messed it up when changing the mixer cartridge. There’s the tiniest slowest leak dripping out the bottom. What be the easiest solution here? Thanks in advance

How would I take a drain line from a washing machine (which pumps the water at a pretty high rate) and insert it in the side of this PVC fitting where the red spot is? This is the final pipe out to the sewer for the entire house. Can I drill a hole and make some kind of waterproof connection...