If this Subdivision requires or allows the regulations to prescribe a period or other time limit relating to a step in considering an application for a visa, the regulations may prescribe different limits relating to that step and specify when that specified limit is to apply, which, without limiting the generality of the power, may be to:
(a) applications for a visa of a specified class; or
(b) applications in specified circumstances; or
(c) applicants in a specified class of persons; or
(d) applicants in a specified class of persons in specified circumstances.