1. Yes, you can have AAM deployed on selected pages of your site or app.
The recommended way is to use Adobe DTM and then apply DTM tag on pages where you want AAM to be deployed. Otherwise, you can implement it with other methods as well.
If it is only a pixel, and not inbound or outbound ID sync, then the pixel code can be applied to any page of your choice to capture custom variables.
2. AAM users are Advertisers, and Publishers both. There are scenarios where advertisers use a pixel not only on their website or app, but they also use it on other platforms or publishers.
Since they want to implement something on your platform, so that depends on you and that advertiser. For c and d, I would recommend you to contact AAM support for more info.
Thanks,
Varun Kalra