I want to remove thousands of pages from my site... Can I remove all the links from site and 410 them....
I cannot submit a sitemap for those pages (as I dont know which pages and how many pages are indexed), so Wouldn't that make them orphan? and having 1000s of orphan pages 410-ed will hurt or wont hurt?
First, a URL is not a link. I think your questions are confusing the two.
1. Yes, you can remove URLs and return a 410 Gone.
2. If you do that, you also want to remove all links on other URLs that point to those URLs that are now gone.
3. A 410 response is not an orphaned URL. An orphaned URL, by definition, is content served with a 200 OK status.
The bigger question is not just "can" you do this, but "should" you. That requires quite a detailed analysis of your situation, what backlinks would now have no target online, whether you will lose much traffic because link equity is no longer being circulated through those removed URLs.