Hi Airam144,
We understand that you'd like to set up individual restrictions on two different devices, and those devices are currently sharing the same Apple ID. As it turns out, the "Share Across Devices" setting will share usage information across all devices that are using the same Apple ID, but disabling it will not free up the option to make changes to individual settings on the devices. This feature is designed to show how much time was used in a certain app or category across all devices that are signed into the same Apple ID; for example, if social media was used for an hour on an iPhone, and 2 hours on a Mac, it would show a total of 3 hours in the Screen Time report. To make individual changes to device settings would require creating a separate Apple ID for each device. We've included some resources below that provide additional information, as well as how to set up a child account using Family Sharing.
Use Screen Time on your iPhone, iPad, or iPod touch
Use parental controls on your child's iPhone, iPad, and iPod touch
To turn the Share Across Devices feature off, you'll need to temporarily disable the restrictions on the Settings app, which will then enable you to make changes.
If you have any other questions, please be sure to let us know!
Take care.