Here we are again (stuck on last two).
17d) When "if..." took place, depicting utter revolution at the end (4-4)
I have ?E?M-?I??, and guess it's TERM-TIME, but can't really parse it;
and
27ac) Variant of 19 originally childish (5)
19ac is ANNE, and I have N?N??. Is it NANCE?
Grrr...