From what I understand, 452 youth and 452 scout are the same. They are a 452 action with 452 trigger, shorter barrel and shorter lop in a beechwood stock. The sights are inferior to normal 452 sights.
The 513 has its own action, it has a lower quality trigger and lower quality sights (same sights as scout) but barrel is full size, stock/lop is full size and stock is also beech.