Grover:
I know of no requirement that an exterior receptacle cannot be on an 'inside' circuit, per NEC. There's a thread here that debates that subject, I don't remember if it was relocated into the "Non-US" forum or not.
IMHO, based on your description, there is no 'Rear'. However, you may decide to install a receptacle (GFI) on the rear garage wall to save any possible greif.
Is this structure still considered a single family dwelling, or is it considered a 'duplex', or two family? If it's a SFD, and a rear receptacle was required and installed when it was built, then that one (1) is all you need.
