Welcome to the Q&A Forum

Using robots.txt to prevent search engine from indexing the page is not a good idea. so what is the sense of robots.txt? just for attracting robots to crawl sitemap?

we're recommended 100 links or less on one page. is the 100 links including header and footer links?

yes, i did 301 redirects for part of the pages. how to move the pages that have been indexed. is it necessary to do 301 redirects for all the pages?

our site has complete redesign including site architecture, page url and page content (except domain). It looks like a new site. The old site has been indexed about thirty thousand results by google. now what should i do first?