If Xyz.com is linking to my page example.com/abcd and my page /abcd is disallowed in robots.txt file. Will page /abcd get the benefit of backlinking from xyz.com
No all that the robots.txt file does it tell a search engine not to crawl that page that's listed in the robots.txt. If xyz.com is linking to one of your pages, the search engine will crawl it from that link. But it wont crawl it from your site.