Below are the steps to stop instagram from saving photos to camera roll:-

1. The first step is to open the Instagram app on your device.

2. Then log in to your Instagram account and then tap on your profile icon in the bottom right corner.

3. Now tap on the three horizontal lines in the top right corner.

4. Then tap on the Settings and Privacy option and then tap on the Archiving and downloading under the Your app and media section.

5. Then finally disable the “Save original photos” option by turning the toggle off.