Upvote:0
Does it mean that if I get to London at 18:30 On may 22, I can leave before 23:59 On may 23 without needing a transit visa?
Yes, that's exactly what it means.
I have an F4 immigrant visa, does that qualify?
Yes, an F4 immigrant visa is a US visa. It qualifies.
I cannot answer the others.
Upvote:0
Does it mean that if I get to London at 18:30 On may 22, I can leave before 23:59 On may 23 without needing a transit visa?
Yes.
I have an F4 immigrant visa, does that qualify?
Yes.
My mother already entered the US with her F4 immigrant visa and she has her passport stamped by the CBP, which means that her visa serves as a residency for 1 year before she gets her actual Green card. Does she qualify as an LPR?
Yes. Your mother became a permanent resident the moment she was admitted to the US. (The immigrant visa becomes a temporary green card when it is stamped with the admission stamp.)