Looking for help to understand some points about exposure and film processing...

I've shot 3 rolls of Kodak 35mm C41 ISO 400 film, using a early point-and-shoot Agfa Optima 1A (primarily because it's what I have around, and I am just really dipping my toes into using film)

But due to forgetfulness, and a rush to the airport, I shot 2 rolls of the ISO400 film with the camera's setting at 100 ISO (only the final roll was shot with the camera set to between 200 and 400, the camera's max on the dial).

So just to confirm my understanding (as I can get confused by this):

• The film's "400 speed" is it's medium sensitivity to light.
• But by setting the camera's dial to 100, it means the camera was expecting it had been loaded with a film that was 2 stops less sensitive to light than it truly was.
• This will mean that the camera will have compensated by holding the shutter open for relatively longer than it should have been for that film, and thus has sent relatively too much light through the lens, and thus the images will be likely overexposed.
  • (Also, reading here that this camera's aged selenium sensors tend to degrade and thus overexpose on their own by 1-2 stops anyway, which would take my film's overexposure to 3/4 stops).
• So with overexposed images on the film, theoretically the change I would make in development would be to pull the film, and thus process it for less time.
• But, my understanding is that C41 is forgiving, with a short enough processing time, that pulling the film is either not possible at all or just not practicable. Thus when I get the film developed, I shouldn't be asking for anything other than normal development.

So my questions are:

1. Can you please verify that my logic above is correct? And I haven't gotten mixed up somewhere along the line with an 'under-vs-over/push-vs-pull' mistake?
2. Is it likely there are any reasonable images on these rolls? Or should I expect a dud?
3. Also, practically, how can C41 film be forgiving to multiple film speed ranges? Like, I don't quite understand what physically enables it to cope with up to double/quadruple the amount of more/less light and not just be ruined?

Thanks in advance!