A fernco or rubber fitting. This made of rubber and had hose clamps on it. You should ask for assistance at a hardware or Plumbing shop for a 2" Plastic X 2" Copper Fernco or rubber coupling.
If the sink/sink drain fitting connection, sink drain fitting/disposal connection, dishwasher/disposal connection, disposal/drain elbow connection are what are leaking they can either be tightened or have gaskets replaced or other sealing methods used. If the disposal is leaking elsewhere the disposal needs replacement.
If you reduce the soil connection to 2" and install a trap
typically shower drains are 2"
If you have a drain available. You may need to chip some concrete around the drain to install the bottom half of the drain. With that in place, set the shower over it and the top piece screws into the drain to form a seal. You can build a 2x4 frame and raise the shower up enough to run a drain to a sump or a floor drain.
2"
If the sink/sink drain fitting connection, sink drain fitting/disposal connection, dishwasher/disposal connection, disposal/drain elbow connection are what are leaking they can either be tightened or have gaskets replaced or other sealing methods used. If the disposal is leaking elsewhere the disposal needs replacement.
If you reduce the soil connection to 2" and install a trap
You can use the existing floor drain lines most likely you will have to cut the drain line or add to it to line up with the hole in the shower. tubs have drains on one end while most showers have it in the middle. You can buy a 30" by five foot base from Mustee. Nice product, comes in left or right hand drain.
Either, but there is usually a rubber washer supplied with the fitting that is better.
From the rim of the drain inlet to the p-trap point of connection 15 inches is what I recall.
Shower drain goes into a trap under shower. Continue piping from trap to drain line.
Water won't drain from shower. Either trap or shower drain line is clogged.
Normally you glue it together. Where it meets steel or copper, you use the proper fitting on the PVC to accept the steel or copper. For steel on the drain, a rubber connection with hose clamps can also be used.
Fitting that holds pop-up assembly tight to drain body, or, tailpiece, needs tightened. Tighten fitting enough to stop leak, not so tight that pop-up assembly won't operate properly.
You could drain the line, sandcloth flux and solder it. Otherwise, see if you can get a compression fitting that would fit the copper tubing
no
YES.