IPv6: truly P2P?

So I head that ISPs usually allocate 64/ IP block per customer. That means, I could access 18,446,744,073,709,551,616 individual hosts of my network, if I allow ports, access on router?

What IP6 prefixes ISPs usually allocate? Do they allow ports?

Regarding ISPs allowing/blocking ports, it would make more sense if they don't, since additional firewalling requires more computational power, which is very costly on gigabit speeds