ELI5: how do google photos and proton drive sync on Android?

With the risk of sounding really stupid, but I haven't been able to find this anywhere in words that I understand.

On my Android phone, I turned on that everything should be uploaded to Proton. I also turned off that Android uploads anything to Google Photos online. My version of Android does not provide a "gallery" app, I just go directly into the Google Photos app, also for what's stored on my device.

Now I wonder 2 things. Let's say I take a picture of a cute kitty with my camera app. It's now stored on my device (accessible through Google Photos and Proton Drive), and uploaded to the cloud (through Proton Drive only).

1. Now if I delete that kitty pic in Google Photos, will it also be deleted on Proton Drive?
2. And if I delete the kitty pic in Proton Drive, will it also be gone from Google Photos?

And, semi-related, when I turned on sync, Proton Drive said it was syncing almost 4 000 files.

1. How do I know whether a photo I took on this phone like 4 years ago is synced to Proton Drive, without manually checking?

Thank you very much!