A convenient tool has long been invented for downloading videos from Instagram without losing quality - story saver. It allows you to get a video in the exact resolution in which the author uploaded it to the network, without any compression or loss of clarity. You insert a link to the post, choose the format and download it directly to your device. No complicated settings or hidden restrictions. Moreover, such a service supports not only videos, but also photos, reels, even stories, so you can save any content you like.
If you want to get the highest possible quality, you should use services or bots that pull the original file from Instagram servers. Then you get the same thing that is available in the application, without additional compression. You just need to understand: Instagram does not give you the "original" in the form in which the author uploaded it. The maximum is the highest version that the social network itself stores.