Upload videos
Yes.

Stream videos hosted in youtube for example
Not possible now, but we are working on this, may be available in next release of after that.

And the most important part is, if i can be able to modify the look (ie. design my own template)
Script is smarty template based, so you can change look and feel.

so it can display the chosen categories in the first page instead of the recent videos and most viewed, for example: I got Category 1 / 2 and 3 and i would want to create 3 vertical columns where i will be displaying 4 videos of Category 1 , than bellow 4 videos of category 2 and on the last 4 videos of the category 3. I would also want to know if i can create sub categories within a category?
What you are asking need script change also, not just template change. If you just need to put links your self, you can do it, but vshare can't do it by itself.