No. The same photon is aware of all alternative paths it can take, without creating or interacting with any other photon. There's no photon multiplication, and

No. The same photon is aware of all alternative paths it can take, without creating or interacting with any other photon. There's no photon multiplication, and no "all other photons" changing their path. There is some inter-photon interaction because they are bosons. But it's not significant enough to impact the multi-slit experiment. And the experiment works exactly the same way if you send only one photon at a time.