While I can't think of any reason why it would, it seems to. When I leave my iPod totally unplugged, it discharges very slowly, only perhaps 20% per day. If I leave it plugged into my Xbox, it charges while the Xbox is on, but rapidly discharges while the Xbox is off, for some reason.
Yes, bu very slowly. Will cause dead battery in about 1 month
It will probably keep transmitting and place a small drain on the battery.
Yes GPS is plugged in and comes on all by itself, it can drain the battery.
leaving on the radio
Parasitic voltage drain. Are you leaving something like an inverter plugged in? If you installed a new car stereo or amp for example and connected to a power source that is "hot" all the time, whatever is on that line will drain the battery all the time.
Anything left plugged in and powered up can drain the battery.
If the outlet is powered with the key off, then yes it will slowly drain the battery.
mainly leaving your lights on when the engine is of or leaving the keys in the ignition
No, not unless the ignition is turned on.
If the engine is running, then no. The alternator constantly keeps the battery charged.
No, the charger pulls so very little power as to not be an issue unless the car was not run for a long period of time. It would take a very long time for the charger to drain the battery.
leaving your lights on for a long period of time.. headlights or just playing the radio and leaving it play for a long time