You need each piece to have a threaded end fitting, one male, one female.
You can't. There is no fitting to do this. Galvanized has to be threaded.
Yes
Pipe dope and/or teflon tape
Depends on local codes and the PH of the water
No, do not use glue. Use teflon tape or pipe dope on the threads. You should also make sure you always put the male PVC thread into the female metal thread. If you do it the other way you will tend to split the PVC fitting when you tighten the threads.
A threaded copper fitting on the copper side, male or female, and the galvanized is screwed into it.
There are no hoses that do this. There is only copper pipe, galvanized pipe, or PVC normally use in a home water supply.
Yes.
It depends on the size of PVC. For smaller PVC you can buy fittings that glue onto the PVC and allow a thread x barb fitting to be installed. For larger pipe you should get a brass compression fitting that clamps down on the PVC and adapts to a thread x barb fitting.
Abs to PVC glue sold at home depot Color it aqua blue/green plumbers key term. GUMBY GLUE Depends upon what you mean by "black pipe". If you mean ABS drain pipe, there is glue for that. If you mean steel "black pipe", i.e., non-galvanized, then you would need a threaded connection adapted to the PVC (either a female PVC connector on a male black pipe or a male PVC connector into a female black pipe fitting). The secondary question would be, "Why would anyone want do to that?"
GI Pipe is "Galvanized Iron" Pipe. These days the pipe will likely be made from steel rather than iron.
There is a coupling that almost all plumbing stores should have(including lowes). Its name can vary but is commonly called a dresser coupling or a raybolt.