If you have a switch connected to a loop you gota put an isolator in your loop best just after the switch. This should stop shortcut message. You will also have to reverse the polaraty of the power supply for the train to continue. It is best to isolate the loop compleatly and to have it’s own power supply.
It´s all digital reversed. Ifyou want you can take a look
The third question: You may install starterkit and 1st expansion and type password only if you lost the partition with RTR(inclusive un- and reinstall) to reactivate al of RTR. 😉