a). Yes, b). That is one of the ways to block access to Tor: either block torproject.org (in which case you use the GetTor service or mirrors), or the DAs, in which case you can't bootstrap. The way around that is to use bridges (unpublished relays to which you connect) or pluggable transports which now come bundled with Tor Browser. (https://www.torproject.org/docs/pluggable-transports.html.en)