So, I installed "Backup and Sync" (the replacement for deprecated "Google Drive for PC") and created an MS Word Doc in the drive folder. I understand that I can edit this word doc from any PC where I have set up and synced my docs using "Backup and Sync".

But what if I want to edit this word doc (saved in my Google Drive from any other PCs that don't have "Backup and Sync"?

I tried to open the doc using online application. It made a copy of the document and changes were saved to the copy only. Is there any way to sync back those changes to the original word document?