Geothermal power can only be used in some areas (apex)

Yes, fundamentally geothermal energy is NOT a renewable resource. The souge heat for geothermal energy is the heat from Earth's core (caused by the fission of heavy, radioactive isotopes). This heat is dissipating and will not be renewed. Also where geothermal energy is extracted, the turnover rate in the crustal rocks is so slow that the heat source is quickly cooled to the point of exhaustion. (Note, highly volcanic areas are an exception to this).

No. Fossil fuels are coal, oil and natural gas. Geothermal energy is a clean renewable energy powered by the heat from the centre of the earth. It is the only renewable energy whose power does not come from the sun.

A waterless ground loop in a waterless earth-coupled closed-loop geothermal heat pump system typically uses a high-density polyethylene (HDPE) pipe. HDPE is a durable material that is resistant to corrosion and provides good thermal conductivity, allowing for efficient heat transfer between the ground and the heat pump system.

Reservoirs of hot water and steam are eventually used up

Geothermal power can only be used in some areas (apex)

steam in the earth

I think to:
- heat from hot springs
- heat from the thermal gradient of the earth

Volcanic IS Geothermal.