Hi there,

Is it possible to show ONLY image and video easysocial Activity stream in frontpage?

Unfortunately, it's not possible with EasySocial 2.x. However, this will be possible in EasySocial 3.0 as shown http://take.ms/xmi3B

and force users must upload image or video when posting?

Unfortunately, this is not possible. However, perhaps you can opt for customization request for this feature.