is it possible to backup MacBook pro to iCloud?

No you can't back up complete Mac data in which system files from user library and system library and applications are also included to the iCloud , to back up Mac time machine is used see the article https://support.apple.com/mac-backup

The iCloud has a different feature , when an apple id is signed in system preferences and iCloud features are turned as on https://support.apple.com/en-us/HT207689

The applications sync and their data that was used saves in iCloud , but for back ups see the complete details https://support.apple.com/en-us/HT207428

Apple offers iCloud Backup for iPhones and iPads but not for Mac computers.

It is possible to sync data from a Mac to iCloud if you turn on those options (e.g., iCloud Photos, iCloud Drive including the Desktop & Documents option). Syncing has some of the benefits of a backup (and the benefit of being offsite) but is not the same as a backup. Major differences include the fact that not everything on your Mac can be synced and the fact that if you delete something, accidentally or otherwise, there is only a limited time period (30 days in most cases) during which it can be recovered.

More information on syncing in:

Set up and use iCloud Photos - Apple Support

and

iCloud Drive FAQ - Apple Support

Okay .