Can idelete old backups except current back up

Hi. yes you can.

How to delete iCloud backups on your iPhone or iPad:

1. Launch the Settings app on your iPhone or iPad. 
2. Tap your Apple ID banner right at the top of the screen.
3. Tap iCloud.
4. Tap Manage Storage under iCloud.
5. Tap Backups. 
6. Tap the device whose backup you want to delete.
7. Tap Delete Backup at the bottom. 
8. Tap Turn Off & Delete.

Hope this helps. Let me know of it works for you.