We have revealed the relationship between quantisation ambiguities in quantum cosmology and the absence of spacetime singularity, deduced the astrophysical observational implications of superextremal Kerr spacetimes and wormhole structures, both of which may be possible under significant quantum gravity effects, and indicated the possibility of particle collision near the horizon of near-extremal rotating black holes of which the centre-of-mass energy might reach the Planck scale.