Quantum dynamics calculations of the title reaction were performed within planar 4D and 5D models to investigate how the dissociation rate is affected by the change of total energy or vibrational character of the initial states. In the 4D calculations, the possibility for observing the mode specificity in the in-plane modes was examined by generating the initial states that are locally excited with respect to specific vibrational modes and comparing the dissociation rates for these states. In order to generate the appropriate initial states, we employed the spectral filter method combined with the zero-order vibrational Hamiltonian in the bond coordinates. Comparison was also made between the dissociation rate and the intramolecular vibrational energy redistribution (IVR) rate. In the 5D calculations, we have focused on the CH overtone excited states and examined how the dissociation dynamics is changed by the total energy that is above or below the dissociation threshold. We observed quite large fluctuations in the time-dependent rate coefficient for the fifth CH overtone state, which was found to occur due to the resonant oscillations of the CH stretching and bending energies as well as the closeness of the total energy to the dissociation threshold.