A Full Fare ticket is the same price, 95,00€, whether it's from the Munich Hbf or Moosach to Zürich. So if you advance purchase a Full Fare ticket, you'd be saving the cost of a Moosach to Hbf MVV ticket, 3,90€. If you purchased a Full Fare ticket from Moosach and then decided to stay one station farther out, in Oberschließheim, the cost of a FF Bahn ticket is 7,-€ more, so you would probably be fined if you got caught.
If you book a Sparpreis (Savings Fare) ticket, the ticket from Moosach to Zürich is 3,90€ more than the ticket from Munich Hbf. 3,90€ is the price of an MVV ticket from Moosach to the Hbf, so you're not saving anything. However, if you later decided to stay in town, within walking distance of the Hbf, you'd have wasted 3,90€.
There was a page (pages) available on the old Bahn website that showed all of the stops included in the City Tickets, but I can no longer find it. However, the fares for Moosach to Zürich say that a City Ticket is included, while the fares from Oberschließheim to Züruch do not. Moosach is in the central (M) fare for Munich (actually, it's a border station, in both zones M and 1). Oberschließheim is outside the M zone. I think that only zone M stations are included in the City Ticket for Munich.