Hello,
You asked for it 🙂
1/ This design is suboptimal because the OSPF initial area number chosen ot be 0.0.0.12, not 0.0.0.0.
If only 1 extra OSPF area need to be added, this will still work fine and Jeff Doyle's book on OSPF and ISIS has an example of 2 nonzero OSPF areas talking to each other.
But imagine what happens if 2 or more extra nonzero OSPF areas need to be added.
With 2 or more extra nonzero OSPF areas need ot be added, then they cannot be arranged in a straight line:
0.0.0.12--0.0.0.13--0.0.0.14. In this fashion 0.0.0.12 cannot talk to 0.0.0.14 and vice versa.
2/ You are asking whether placing a link between 2 access routers in same 0.0.0.12 area is correct.
If this link is placed in a separate nonzero area, then it is clearly incorrect, because this link will never be used. The reason can be found in RFC 2328 : Type-3 LSA received over nonbackbone interfaces are ignored.
3/ I hope the lnks are properly sized because if one Core Router-Access Router link fails, then the remaining Core-Access link has to carry double or even triple usual amount of traffic.
HTH
Thanks
Alex