Time machine - delete old backup

suppose I had 2 backup files:

Jul 1st: 20GB
Jul 2nd: 1GB

Now what would happen if i permanently delete the first backup file 20GB and restore only the second one which is only 1GB (i assume that would save some capacity for my external hard drive). does Time machine work that way? because when the hard drive fills up, TM will automatically delete the old files anyway.
Pls correct me if im wrong. Thanks

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and btw, do you know any app that allows me to schedule the backup? because i dont want TM to back up every an hour, but 24 hours for example.

 

that would do the trick. thank you