What year did BMW start putting reverse opening hoods on their vehicles?

This depends on what you mean by reverse opening. BMW switched between forwards and backwards opening hoods over the past 30 years. There was no single change across all models. I don't know if there's a specific pattern but almost all the recent ones have a rear hinge that opens to the front of the car. Here they are.





E31 8 series rear hinge





E23 7 series front hinge


E32 7 series front hinge


E38 7 series rear hinge


E65 7 series rear hinge





E24 6 series front hinge


E63 6 series rear hinge





E12 5 series front hinge


E28 5 series rear hinge


E34 5 series front hinge


E39 5 series rear hinge


E60 5 series rear hinge





E21 3 series front hinge


E30 3 series front hinge


E36 3 series rear hinge


E46 3 series rear hinge


E90 3 series rear hinge