Are these sitemaps necessary to make for a website and i also wanna know that the purpose of all these. i just make two sitemaps (XML Sitemap, HTML Sitemap) for my website to whom i know the purpose.
Text Site Map (urllist.txt)
ROR XML Site Map (ror.xml)
Mobile sitemap
News sitemap
Code sitemap
An html sitemap will normally be a page on your site that helps users find what they are looking for. An XML sitemap is usually placed behind the scenes and is there to help search engines index all of your pages.
I never heard or read about code sitemap.
In my opinion, Sitemap that are important for a website are
XML Sitemap
HTML Sitemap
Image Sitemap
Video Sitemap
Mobile Sitemap
Two types of Sitemaps are there 1. HTML Sitemap - For human 2. XML sitemap- For Search Engine’s Robot.The purpose of sitemap is to getting your Webpages into the Google index. The search results provided by Google are from their index. Since 85% of the Internet happens as the result of a Google search, being well indexed can be a good thing. but if u have so many pages and if you did your internal linking structure properly, there is no need to submit an XML sitemap to Google.
each sitemap has different purpose and as per my knowledge HTML Sitemap is for human to help in navigation, XML Sitemap for letting search engine know about all of your link that are present in Sitemap
video and image sitemaps are good if your website is heavy on those and you want to help Google a little 
The HTML sitemap is kept for the user-navigation. If the user wants to go a particular URL he can directly go to that page using HTML sitemap. The XML sitemap is generated for the search engine bots. The XML sitemap that can be submitted to Google, Bing, Yahoo and other search engines to help them crawl your website better.