If there are three attachment points then you have a ground and two hots. The ground goes to the green screw and the hot wires can be connected to either hot screw. If there are four wires then the hots will likely be red and black. The white wire is the common or neutral and the green or bare wire is ground.
You don't, at least, not legally.
No it is not
Wall receptacles are wired in parallel. black to black, white to white, ground to ground.
The hot wire's cover is smooth and connected to what I call the "button" at the bottom of the socket. The neutral wire's cover has ridges and is connected to the screw shell of the socket.
You'll need to contact an electrician who will pull a new wire for you. If you only have 2 wires on the 240 line, you don't have a neutral or a ground; both of which are essential for a modern electric range.
To convert a 4-wire 220V connection to a 3-wire 220V connection, you will need to remove the neutral wire and connect the ground wire to the neutral terminal. This diagram shows the proper wiring configuration for this conversion.
The recommended wire size for a 220v electrical circuit is typically 10-gauge wire.
2 gang
You don't, at least, not legally.
No
No.
The recommended wire size for a 220v 20 amp circuit is typically 12-gauge wire.
The recommended wire size for a 220v 30 amp circuit is typically 10 gauge wire.
The appropriate wire size for a 20 amp 220v circuit is typically 12-gauge wire.
The appropriate wire size for a 220v 30 amp circuit is typically 10 gauge wire.
The recommended wire size for a 60 amp 220v circuit is typically 6-gauge wire.
The following applies to the UK Blue wire goes to neutral Brown wire to live Yellow/Green stripe wire to earth