It is called Brazing rods or lead free solder
Yes, epoxy will stick to cured epoxy.
it is poo
Yes, polyurethane will stick to epoxy when used together in a project.
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.
I wouldn't, it will not stick well.
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.
No, a magnet does not stick to copper because copper is not a magnetic material.
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.
Epoxy resin can stick to a variety of materials, including wood, metal, glass, ceramics, and certain plastics. It is known for its strong adhesive properties and ability to create a durable bond with different surfaces.