Which permission is required to post on facebook main wall or timeline through personal website c#? like pages_read_engagement,pages_manage_posts is required for posting on Fb Page
By “main wall” you mean the user profile timeline?
That is not possible any more via API, that has been removed a while ago.
https://developers.facebook.com/docs/graph-api/changelog/breaking-changes#login-4-24:
The publish_actions permission has been removed. Apps that have already been approved for publish_actions can continue using the permission until August 1st, 2018. If you want to provide a way for your app users to share content to Facebook and Instagram beyond this date, we encourage you to use our Sharing products instead.