I too agree with Haggis an GrumpyBob. Any DCC layout should be wired into electrically isolated 'blocks' called Districts. An electrical district is nothing more than breaking the layout into managable pieces for trouble shooting problems and independent operation. The other benefit is if something shorts in section A, sections B-F won't be effected by the short.
The most common short is running the points of a switch not lined for the route you want. In DCC a short is detected by the Command Station. It shuts down to protect itself and the place where the short has occured. It also protects against damage to your engines, track, metal wheels, etc. So if you have your whole layout wired as one power district, the whole layout goes down. Whereas, if you divide it up into smaller power districts, when it shorts in one district it won't take the whole railroad down with it. So you can see where this would come in handy.
Reverse loops in DCC work the same way as in DC. They both can use a DPDT toggle switch to change the rail polarity. The advantage with DCC is you can buy an automatic electro or electro/mechanical reversing modual to do this for you and do away with the DPDT toggle. On my NCE Command Station there is one already built in to use. You can buy reverser moduals from MRC, Tony's Trains, NCE, Digitrax and some others. The MRC is a low cost, reliable, and easy to install reverser modual. To wire one up, you isolate the reverse loop like you would on regular DC and gap both rails into and out of the loop at the turnout. The reverser has 4 wires. 2 go to the 2 rails (or power buss) BEFORE the turnout, and the other 2 wires go to both rails of the loop after the gaps. Pretty easy.
Hope this helps.
Bill S.