Basic water pipe repair / 14 oz cylinder, extension / tools

https://www.ebay.com/itm/Char-Broil-4-Ft-Hose-Adapter-Pressure-Propane-Extension-Bottle-Camping-Stoves/253873816047

https://www.lowes.com/pd/Worthington-Pro-Grade-14-1-oz-Pre-Filled-Propane-Tank/3082795

https://www.ebay.com/itm/Mag-Propane-Pencil-Soldering-Torch-Pencil-Frame-Tip-Burner-Torch/190687333241

I may need to solder a copper pipe near a wall (DIY repair). It would be in such a place that it’s hard to get to (hence the extension hose, to keep the cylinder upright). Some questions:

  1. Are those three items compatible?
  2. About how many joints can one expect to be able to solder with one of those cylinders?
  3. If I spray water on the surrounding walls, is it pretty much highly unlikely to cause a fire?
  4. Once the tip is installed onto the propane cylinder, can it be removed, or do I have to keep it on there until I use up the cylinder completely?
  5. What if I need to repair a black iron pipe? Can a fitting be soldered onto a broken black iron pipe as well?
  6. Is it possible to solder a brass fitting onto a black iron or copper pipe? How would the process differ from copper-to-copper soldering? I ask because it would be really convenient to repair a long stretch of broken copper pipe by soldering a pex fitting onto the pipe and running pex up the wall.