Photo management on iCloud and Devices

Set up photo library in iPhone Set up and use iCloud Photos - Apple Support

1. Delete photos on my iPhone to reclaim the space (without deleting them on iCloud)

It's not possible when photos are synced with iCloud , when you delete photos from the device they get deleted from www.icloud.com .

What happens when you edit or delete photos

When you edit or delete photos or videos, the changes are reflected across all of your devices.

Edits show up on all of your devices

When you make edits in the Photos app on your iPhone, iPad, or iPod touch or on your Mac, the photo automatically updates across all your devices, including your Apple TV. So when you crop or enhance a photo from your iPhone, you see the changes when you access your library from your Mac. Your original photos and videos are stored in iCloud and you can go back to them at any time, and revert any changes you made.

Photos delete from all of your devices

When you delete photos and videos on one device, they're deleted everywhere that you use iCloud Photos. If you delete something accidentally, you can recovery it in the Recently Deleted folder for 30 days. After that, it's deleted permanently.