intact Yes, because the gallery is for images. You should see a button with a video camera icon next to it: “My media”. Click that, then the Upload button at top-right, locate the file on your device, and upload it. When it finishes uploading, select it to add to your post.
All standard file types are permitted. I think the max filesize might be 100 MB but you should be well under that for that short clip.
