On the same WiFi network yes you can - it uses the same MAC on the same SSID. Remembers the "random" MAC after the first connection (and if you first connected to the networks before they added MAC randomisation in iOS14, it "remembers" the actual MAC of the device, so you didn't have compatability issues after the iOS14 upgrade).

So you can't use it to track devices between multiple SSIDs including when scanning for networks, but you can use it to persistently identify a device when connected to the same network.

You misread the question.

Yep, you're right. Agree with the other post - the randomly generated MACs have no manufacturer info.

Other than perhaps the manufacturer from the OUI, no.

There’s no manufacturer in a randomly generated local OUI.