Oxbridge Rowing

Hi, I was wondering if I could ask a few questions purely as a swimmer from America interested in the sport of rowing - I hope it's not too much trouble.

First, I was wondering if it's actually possible with the level of the first boat for someone to train for 2-4 years and make it to the top boat. It seems like a tall order and although I'm sure the developmental team is incredible, is it really possible? (say, even if they are in good shape from another sport) .

Second, I'm curious about what kind of ERG times the top rowers on the first boat can achieve over 2k and 5k. I'm curious how the data matches up across programs.