From my experience 2 months ago:
1. Yes, you've got to get in the photo line after each ride - presumably they don't keep the photos around in the system forever if no one claims them. In our experience though, the Universal photo lines were much quicker than the Disney photo lines.
2. I think they were all 5x7.
3. We did the prints as we went for ride pictures, since we had to stand in line anyway to give them our card, but did the character & other pictures at the end of each day. On the last day, we went through all the pictures and found any we had missed and had them printed, and this wasn't a problem, so I'm sure you can do all of them on the final day. Forbidden Journey is the exception - they told us you had to go to FJ to get FJ prints - couldn't get them anywhere else. Even then, we were able to get FJ prints from previous days, since we didn't buy the print package until day 2.
So you have to add the ride photos to your card after each ride, but prints are at your convenience.