It is called Brazing rods or lead free solder
it is poo
I wouldn't, it will not stick well.
Galvanized pipe will be silver/gray color. Copper will be copper. Use a magnet, it'll stick to galvanized pipe but not to copper. Drinking water lines should not be black steel pipe.
Epoxy glues would be best.
A metal epoxy is an epoxy that will glue matals. Two good ones are J B Weld and Pow-R-Stick.
Epoxy adhesive can stick to almost anything except some PTFE's and some of the new polyethylenes. It can stick to metals, woods, most plastics (except the fore-mentioned) and stones and rocks.
Epoxy is best for that.
Epoxy or E6000 would be nest. White glue won't stick to the jewellery.
Super glue or epoxy.
Epoxy or silicone glue will do it
No.
It means shooting the puck in hockey into the goal (used to be called the pipes)