With single point fuel injection, when does the injector open? Does it open just before each inlet valve opens, so you get one squirt per cylinder? Or does it open, say, once every few milliseconds and the cylinder just draws in whatever's in the manifold?

I had a VW polo (1991) with a mono point system and the injector sprayed fuel onto a load of cast 'spikes' in the inlet manifold and the injector was continuously running on a PWM type system. Really simple

By single point do you mean 1 injector for all four cylinders (i.e. only one injector in the system) or do you mean one injector per cylinder (i.e. four injectors per four cylinder motor)?

Really just an injection carburettor timing isn't an issue

Injection timing barely makes a difference on port injected engines, less so on mono point!