Hi @Sajith Gopalakrishnan Hema ,
Do you mean that you want to make the sync between the Document Library and the OneDrive folder in one direction? That is, files updated can only be synced from the SharePoint Online Document Library to the OneDrive folder, but not from the onedrive folder to the document library? As per my knoeledge, there is no setting to configure one-way sync. If you don't want some end-users make changes to some documents, you can set file permission or folder permission (Edit or Read) in OneDrive or SharePoint to control it.
As to your second question, I think this can be achieved by integrating with Power Automate Flow like below. There is a dedicated forum Microsoft Flow Community for the Microsoft Flow related issues and questions, I suggest you post a new thread there for further help if you have some advanced requirements.
----------
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.