How does siRNA work in a Dicer-knockout cell line? Also: how does suppression/cleavage decision work in practice?

1. More specifically: what loads the siRNA onto RISC when Dicer is not present? I do know siRNA works quite well without Dicer; I just can't find any information on RISC loading in systems where Dicer is missing.

2. It's clear that only Ago2 can cleave mRNA; and that a complete match of the guide strand with the target will cause mRNA degradation as opposed to suppression. But herein lies the question... How does the small RNA "know" which RISC to be loaded onto? We only have one Dicer, so Dicer homologues can't determine the loading. I'm not sure if Dicer "remembers" what kind of RNA it processed into small RNA. Do other, RNA specific proteins "decide" which RISC complex gets loaded? If so, how can miRNAs induce cleavage if they happen to be perfectly complementary to their targets if they are loaded onto the "wrong" (non Ago2 containing) RISC?