2008 Mini Cooper

1: key needs to be turned so wheel is not locked and thats going to mean a fuse or battery cable has to be pulled so battery won't drain.
2: I don't know
3: I use separate light with magnets that are wired to RV.

You turn the key to the first position that unlocks the steering wheel. That will turn on some things in the car that will drain the battery. Some people pull certain fuses or pull battery cable off.

Wiring a dedicated fused and ideally an ignition relay signaled 12v wire supply to the toad battery will keep it charged.

There are several lighting choices, look up sites like Roadmaster or E-trailer to see options

1- My 2013 Mini doen't have a steering lock so can't help there.
2- Don't do anything other than hook it up and drive away.
3- I used a magnetic light as FarmBoy666 describes. It works quite well on our Roadster. There is a sending unit that plugs into the RV towing connector and a receiver in the light. Tow Mate Towing light This one will work off of 12v of the car or also has an internal battery that can be charged and run that way. Our car (as likely yours does) has a 12V plug in the boot/ trunk.