Why do we need IBGP in AS1?

There are two Border Routers in AS1, IBGP is needed for communication between R11 and R12

Can AS3 communicate with all other networks, if the link between R2 and R3 will be deleted?

No - link between R3 and R7 uses the private peering. R3 can send the packages to 7.0.0.0/16, but not for other prefixes.

→ Private Peering

Mark all entries, that can’t be a part of routing table of R2 in tis network

Fill routing table of R11