(1) is indeed a use-case, unless you require more detailed control over playback/pause/frame numbers. In which case a series of png images (for example, encoded into a .css) and animated using javascript could be used. Google uses this for their doodles.
I think (2) is not really a good use-case. GIF is a terrible, terrible format for movies because of the crappy quality and inefficient interframe encoding. Just use a movie format, they're also good at low-res low-bitstream.
I think (2) is not really a good use-case. GIF is a terrible, terrible format for movies because of the crappy quality and inefficient interframe encoding. Just use a movie format, they're also good at low-res low-bitstream.