How is fuel stored and routed on a trijet with one engine at the tail?
(Own work based on MSFS)
On an MD-11 the tail mounted engine is fed from tank 2, which is two halves as shown above -- the two halves are connected via vent lines.
Sequence
The center tank on an MD-11 is called aux, and it feeds all the engines until it's empty -- the aux tank actually fills the other tanks and the other tanks do the feeding (systems display shown below). Tank 2 (being bigger than 1 or 3) then carries on filling tanks 1 and 3 plus feeding all the engines. Once tanks 1, 2, and 3 have the same fuel quantity, each tank then feeds the respective engine.

(Own work based on MSFS)
Stabilizer tank
Fuel is transferred to and from the stabilizer (tail tank) to manage the CG. It is fully consumed by the time the plane reaches its top of descent -- as a forward CG is more economical for descending. The exact sequence is managed by the fuel system controller. The tail tank also feeds the tail engine as part of the CG automation.
The sequence (and scheduling) is automated even with an engine, or even two, out.
Summary
The #2 engine is fed by the aux, tail, and #2 tanks. If an engine fails, then cross-feeding is involved.