If there is no neutral available you cannot, unless you use an autotransformer and derive a neutral. A panel with no neutral is called a power panel and is used to supply 240 single and three phase loads.
No, pull in a separate feed for the single phase receptacle.
Assuming there is no neutral: 1) Turn off the breaker. 2) Disconnect 1 of the 2 hot wires from the breaker and connect it to the neutral bar (Recommend phase taping the wire white :) ) Remember which wire you used as the neutral, in a home you will most likely have a black and a red. I would keep the black hot, and phase tape the red wire white. If it's not long enough you can wire nut another white wire onto it to make it reach the neutral bar. 3) Leave the breaker OFF, at the receptacle, change it to a 120 volt receptacle. Take the wire you made the neutral, and connect it to the white screw on the 120 v receptacle, and take the black to the hot. Ground to the ground screw. Make sure you phase tape the red wire at the receptacle white as well. 4) turn the breaker on 5) test the receptacle with a meter or receptacle testing device for correct wiring.
I have never seen a four pole circuit breaker. Breakers are single, two and three pole. Single pole for 120 volts, two pole for 240 volts and three pole for three phase loads. In North America all neutrals are SN (solid neutrals) and are not switched. In certain applications using a three phase Y-connected load, where complete isolation of the load from the supply is required, the neutral line connects to one pole of a 4 pole circuit breaker.
No, you should not install a 30 amp circuit breaker to a machine which normally requires a 20 amp supply. The circuit breaker is protecting the wire to the machine. That wire is likely only rated for 20 amps, (# 12 awg). Therefore, a 30 amp breaker could allow too much current to go through the wiring to the machine and cause the wire to burn down. Replace the 3 phase 20 amp breaker with the same amperage breaker.
If you have single phase now, you have two options. One, is to install a three phase service or Two, install a roto phase device.
The job of a breaker is to limit the amount of current that is applied to the size of wire that is connected to the breaker.
Probably
You should step down your voltage source, to do so, a 230V-110V dry type transformer is needed. There's another way of doing it, .. But it is very unsafe.... you just simply connect 1 conductor to the Ground.. but it is not applicable if your line to ground voltage is already 230V...
50amp but if considering the breaker cannot withstand starting current you need to size the breaker up.
A two pole breaker protects both L1 and L2 legs. An over current on either leg will trip the breaker.
10amp
The circuit breaker is sized to the full load amps of the motor times 250%.