You can file for AB before registration of FIR but those cases are very rare.
Courts gernerally don't grant AB prior to FIR.
It is wrong that police will not grant you time after FIR as police is bound to obey the order of SC.
It is clearly written in judgement "Our endeavour in this judgment is to ensure that police officers do not arrest accused unnecessarily and Magistrate do not authorise detention casually and mechanically."