No, however, if copper pipe is going to be chased into the wall and plastered over, you need to use the highest graded copper. (class 2 or 3)
Steel will corrode as the iron in it is more reactive than copper.
You cant, you have to remove the section of piping and install a new section of piping.
Yes, if you're talking about a water softener, you can use copper piping.
Sounds as though you have galvanised piping. Your only solution there is to take the section of piping out and inspect it at the next joint and see whether the condition of the piping is adequate. If not take out the next section of piping until you find that the piping is in better condition. My recommendation is to replace with copper, for two reasons, copper does not corrode and is easy to install. Would be advisable to replace the stopcock and even in some cases the tap as well.
The process of copper re-piping is basically replacing all iron piping in a home with that of copper piping. Unless a homeowner knows how to do plumbing applications, a professional plumber should be hired.
elements and compound
Copper, although plastic piping is preferred nowadays.
Copper piping and wiring and not interchangable.
The question si superfluous as copper piping is NOT used in water wells.
they will corrode
Yes. Use a threaded fitting, male or female as needed on the copper and screw the galvanized into it.You must use a dielectric fitting to connect copper to galvanized pipe. If you don't, a galvanic reaction will occur and the piping will corrode and leak. You can use a Dielectric Union or a Threaded Brass fitting to join the two types of piping together.UNIONS can leak the best answer would have been a dielectric nipple
you solder or braze it