1.
If I want to watch live pictures via Internet, do I need a PC computer with attached cameras which has routed (public) IP address?
No, for watching live pictures via Internet, the PC computer with connected cameras does not need a routed (public) IP address. The PC can be connected via modem (with dynamic IP). The PC can access Internet via LAN with dynamic or permanent (no public) IP. For watching cameras connected to computer behind LAN Your Camera uses ?forwarding?.