You're relying on Hotmail to push email to your PC.
Instead, use a third-party email reader, such as Thunderbird, which polls the Hotmail server at any interval you set, per account. However, should the Hotmail server send notification, the email reader should also display the message immediately, as shown in the settings below.
This is a good question. It would require being able to create a list of the (filenames of the) photos in Google Photos, and comparing that list to the photos you have in Google Drive.
I can point out other useful information (which doesn't answer your question directly). Firstly, I think that if you synced Google Drive with Google Photos before July 2019, ...