You can take a screenshot of almost all the content on Instagram without the other person knowing about it. The disappearing images and videos are the exception where the other user will be notified about the screenshot. The Instagram screenshot notifications policy is not stringent at all and you can freely take a screenshot of whatever content you like on Instagram and the other person will not have any idea about it. You must keep in mind that Instagram changes its screenshot notification policy from time to time. So, you need to stay updated