2) depending on what you mean with "photo manipulation" the included ShowGirls (under Apllications) offers some basic tools

3) that is supposed to be possible with the ported Blender, just don't ask me how. There might be simpler tools for just converting, cutting or joining videos

5) Samba/SMBFS is supposed to work

6) VNC is the way to go here

9) not sure if http://kaczus.republika.pl/newscoaster/ can do this

Just a small hints:

If you want to register for a G4 PMac, better make sure that you have a descent GFX (Radeon9000 with 64MB or better) and CPU (you really want something with atleast 1GHz) at hand. Just getting those alone can be harder than getting a full PMac in that configuration.
Ideally you either buy a MDD/FW800 which came with those specs as defaults, or an OuickSilver (or older) that allready has been upgraded by the previous owner.