conditional chain linkage with "if but only if"/double arrow

Hi guys,

So I know that for example A ---> B (--|--) C leads to the inference A (--|--) C, whereas A (--|--) B ---- > C leads to no useful inference. What about the double arrow? i.e.

1) A (---) B ---> C

2) A ---> B (---) C

my gut tells me in both cases its just A --- > C but I'm not 100%. Can anyone shed some light on this?

Cheers