This depends on the size and the location of the leak. It depends because a leak on the straight piece of the pipe will differ from a leak on the joint of the pipe. It also depends on the corrosion of the pipe and the extent as to how bad it is.
Cast iron is not threaded, steel pipe is.
Male to female threaded adapters.
For supply, it is copper and galvanized iron. For waste, ABS (plastic) or cast iron.
Demo a section of the wall.
You can recycle a cast iron sink at your local recycling depot. For example, Miller Waste offers citizens to bring their cast iron sink to the depot for recycling for a fee.
No, not necessarily. Most likely the drain has become rotten because of something acidic going into it. Vent pipes usually have a good flow of air in both directions. I would just change the bad waste pipe(s).
If it's threaded, yes. Fittings are usually difficult to remove because of rust and build-up on threads.
1/8" - 10" threaded Cast Iron 11/2" - 15" Copper 1/16 - 10" These are the most common sizes
Waste - Vent - water supplyMaterialsCopper - Cast Iron - plastics
You must break or cut the wall at that point. No other option
Yes. It is simply a threaded male adapter. But what are you trying to accomplish? what you are trying to do may not comply with code and may create a health hazard.
Iron, cast iron is just iron