If I delete my photos which was already uploaded on my icloud will it reflect on my icloud?

Yes. iCloud is a synchronization service, not offline storage. You can reduce the size of your photos on device by optimizing your library (settings > photos)

Make sure that your device is not in low power mode, connect it to power, and lock it.

You can check the cloud status in photos.

Open photos

Tap library

Scroll to the bottom

You'll see the item count and cloud status

Your device may not have synced. The only items in iCloud are also on your phone and vice versa.

I deleted over 1000 photos from my iPhone. They are STILL showing in the cloud. How do I force a sync?