No matter what your reason for raising them is, you will get better results if you give them proper housing with enough room to get away from each other. Keeping them housed in too small an area leads to stress and injuries, which in turn leads to disease, losses, and reduced production. You...
To be absolutely certain without a blood test I'd say point of lay or crowing, which for my Leghorns was 18 weeks.
ETA: But if you notice any growing pointy feathers on their necks or lower back, or the tail feathers curving down before that, you can be certain that one is a male.
I can't tell from the pictures, but usually by this age the males will weigh more than the females. If any of them are noticeably heavier or larger than the others, they are probably male. If I remember correctly, white Leghorn pullet weight at this age should be 85-90% of the males.
I would make sure that you have enough space for them. If they are pullets and are fighting, it's most likely a space issue. And leghorns don't have gaps in their feathering like that normally.