Picture #4 is too blurry to see the tail and anal scutes clearly. Can you get a clearer picture of that one? The animal in picture #4 looks very small, probably too small to determine sex accurately.
Picture #5 looks male to me, based on the large tail and plastron curvature. However, this guy is also small, so I'm not 100% confident with a sex determination at this size.
Age is impossible to determine since stars will grow at different rates depending on both genetics and environment. The size suggests that they're both juveniles.