I would say pic #2 is more along compare to the other two. But all three still have still some time before they give birth.
About how much time?
When they become "squared." Through personal experiences, when my guppies are about to give birth. Their stomach look drop when I look at them when they face me. Hope this make sense.
Do they actually look like a square?
I can't really described how the "squared." When you look at the guppy directly, you can see the drop stomach. Other sign is isolation and not eating.