For example - I have created a file named Test.txt. I got synced and backed up to my onedrive. Well enough good. But after that I deleted it. I didn't got deleted on the onedrive. It stayed there. I want it to sync and delete that file too on the onedrive if i deleted it from my pc
sync is the right thing to do here. For your example deleted in source Test.txt will be deleted from destination when you do another sync.
I would suggest you do not sync all C: drive - it contains a lot of stuff like temporary files etc.
I would only backup what is important e.g. your home folder
Also it is not really backup but only copy of your data. When you delete some veryImportant.doc file and then run sync - it will be also deleted at destination. No more veryImportant.doc anywhere. To run backups you should consider some proper backup software. rclone is not really it.
See to check if something is deleted or not I see from my pc the file that I have deleted then I check the onedrive and then see that the file still remains there. Yes I have tried again by deleting an item and it is not deleted from the onedrive
I can share my screen with you no issues at all. How would I show you my steps in this forum like just by screenshots ? Yes I can be also doing some mistakes I totally agree but I don't know what mistake. I will also learn from my mistake if I get to know it.