If I have photos on my iCloud but not on my iPhone and I turn on syncing again, will the iCloud versions disappear?

If I have photos on my iCloud but not on my iPhone (from a previous syncing, but I turned it off) and I turn on syncing again, will the iCloud versions disappear?

For context, I turned off syncing on my iPhone because I didn't want to get photos from other devices or have my phone's photos sync to other devices.

But then later I realized that I'm missing probably half of my photos! (Which was probably when I had the low res photos since the higher resolution photos were uploaded to iCloud... I didn't get any warning or anything that those photos might get deleted when I turned off syncing.)

I logged onto the iCloud website and sure enough, all my previous photos up to a certain date are all there.

I'm scared that if I turn on iCloud syncing again (to update my current photos to upload onto the cloud), that it might update & delete the said photos on the cloud because my phone no longer has a lot of those photos anymore.

[Edited by Moderator]