You can't.
Just type this: <img src="yourgifurl.gif" />.
A moving image.
Step to start making your own GIFs through the Tumblr app: Compose a New Photo Post in the Tumblr Select a Video or Photo Burst Marked with 'GIF' Edit Your GIF Publish Your GIF
Whether or not it's blurry depends on the quality of the gif.
Yes.
Yes, you can have both a picture and a GIF on Tumblr at the same time. You can upload them in a single post by combining them or by adding them separately. Additionally, you can create a post that features a GIF as the main content and include a still image in the caption or as additional media.
Your GIF is most likely not moving because it is too large for Tumblr. Tumblr GIFs have to be under 500mb or else they won't move. To remedy this problem you can try resizing your GIF to a smaller size!
Well I seen a gif of him on tumblr smoking pot but I'm not sure if it's real or fake.
Change the .gif file to a .mov file
.tumblr.com
Tumblr URLs can't start or end with a hyphen.