1). Acetals and ketals are hydrolyzed under neutral conditions, but very slowly. In this case, DDQ somehow accelerates (catalyzes) the neutral hydrolysis by behaving as a H-bonding acceptor (and indirectly, as a proton acceptor).
If you draw the mechanism of acetal or ketal hydrolysis under neutral conditions with and without DDQ, you will immediately clarify by yourself, the role of the DDQ-water dimer via H-bonding.
2). The selectivity is due to the steric hindrance of the opposed spiro-ketal that inhibits the approach of the DDQ-water/H-bond dimer.