Lots of penetrating oil and / or carefully heating with a flame.
Yes, they can be opened for routine sewer and drain and leader cleaning
Normally right hand threads BUT many times the cast iron female threads are corroded or damaged thus one uses a fits all plug which is lead and tapped into place not threaded
Rusted cast iron.
4" is the standard house sewer main
To scour them use a water Jetter as it removed years of build up soap scum and grease deposits and scale.
Water mains. Sewer line.
Concrete and cast Iron pipes are made of cast iron and plastic piping systems normally use plastics
You don't ... You do melt the material inside the hub
The cast of How to Clean a Cast Iron Pan - 2012 includes: Ahmed Khawaja
Yes. If you were to clean to iron before cooling it, you could risk burning your hands.
A rubber Fernco or Clamp All
By cutting in a cast iron Wye so the flow enters the sewer line (soil pipe) at a right angle