With key K1 closed, C1 and C2 are in series with the battery in steady state.
∴ Cnet=1μF or q0=CnetV=20μC
With K1 opened and K2 closed, charge on C2 will remain as it is, while charge on C1 will oscillate in L−C1 circuit.
ω=1√LC1
=1√0.2×10−3×2×10−6
=5×104 rad/s