How can i edit the photo that already backup?

1. Import them in your pc.

https://support.apple.com/en-us/HT201302

2. During that import remove from the phone.

3. Backup to icloud without photos 3 times and you are all set. (icloud keeps last three backups)

I must have misunderstood original question, what you are trying to ask is "how can I look inside of icloud backup" right?

if yes then you can not. So when you understand that you would still benefit from following my instructions, cause once you

take photos and videos out of equation you will have enough space.

In addition to backup icloud also syncs info and synced notes and contacts can be found in www.icloud.com