All options are correct, (a) ONCl=8+7+17=32e− ONO−=8+7+8+1=24e− not isoelectronic
(b) The central atom is sp2 hybridised with one lone pair. (c) It is a pale blue gas. At −249.7∘, it forms violet black crystals. (d) It is diamagnetic in nature due to absence of unpaired electrons.