Move 17: N a4-c3 doesn't seem legal, but N a4-c2 would be legal.
It looks legal to me. Why wouldn't this move be legal? Meanwhile, a4 and c2 are along a diagonal, and N a4-c2 would definitely be illegal.
Move 25: N f5-c4 doesn't seem legal in same way, but N f5-d4 would be legal again.
N f5-c4 is a perfectly legal Knight move, and I see no reason why it would be illegal. Meanwhile, f5 and d4 are diagonally adjacent, and N f5-d4 is clearly illegal.
When you're examining the moves, be sure to click on Record, paste the moves into the box, and click on View. This will let you view each position. I think you made some wrong judgements, because you got confused about how notation for this game works. Vertical movement shifts to an adjacent file as it goes between the 4th and 5th ranks. So, the space immediately above d4 is e4, for example.
It looks legal to me. Why wouldn't this move be legal? Meanwhile, a4 and c2 are along a diagonal, and N a4-c2 would definitely be illegal.
N f5-c4 is a perfectly legal Knight move, and I see no reason why it would be illegal. Meanwhile, f5 and d4 are diagonally adjacent, and N f5-d4 is clearly illegal.
When you're examining the moves, be sure to click on Record, paste the moves into the box, and click on View. This will let you view each position. I think you made some wrong judgements, because you got confused about how notation for this game works. Vertical movement shifts to an adjacent file as it goes between the 4th and 5th ranks. So, the space immediately above d4 is e4, for example.