How do I recover old iPhone photos deleted over 30 days ago?

“Is it true that iPhone photos deleted over 30 days ago (in the Recently Deleted folder) basically cannot be recovered, especially if there was no regular backup? My dog at home passed away yesterday, and I wanted to look at old photos on my old phone, but it seems that since iCloud sync is enabled, deleting photos on the new phone made them disappear everywhere. 😢”

[Re-Titled by Moderator]

Original Title: iPhone photo deletion