Can't answer the first question. On the second question the answer is "yes". You are supposed to get a written note from train staff to confirm the delay (they scribbled something on my ticket last time it happened to me), but I'm sure they realise that that's not always possible, and I would assume that they will make their own enquiries to verify the delay.

Another thing is that if a train you are booked on is delayed by more than (I think) an hour, and there is another train scheduled before then, then you are allowed to get on that other train rather than wait for your original train.