Electric power is measured in watts. It does not matter if it is single phase or three phase. All things being equal, for the same load, the power measured in a single phase circuit or a three phase circuit, will be the same.

Very unlikely. Its 3 phase for a reason, it needs a large voltage/current to power it, single phase won't provide that.

You would use a single-phase induction motor if the available electric power supply is a single-phase one. That applies to the average house or small business.

All high-voltage distribution systems are three-phase. Single-phase 'spurs' off the main line, supplying, for example, farm houses, are simply two lines of a three-phase system.

In Europe they have both single phase and three phase.