You can add Adsense codes on all pages and posts in your website except where there is no content or very little content. You need at least 300 words on the page/posts if you want to place Adsense codes. You can place adsense codes on about page, even on privacy and terms of use pages. However, you cannot add Adsense codes on contact page login or register page (there are no contents on these pages). If you add adsense codes on empty pages or on the pages with little content, you will receive a violation warning. While this issue does not ban you but you should not take risks.
While using Adsense on your website make sure your content is Adsense safe. You are not allowed to use Adsense on the websites that have a lot of pictures of women wearing bikini, or the content related to pornography, gambling, weapons, alcohol etc.