I have actually heard (and researched) Sapphire Gems. Gorgeous birds, for sure! I wouldn't be too concerned about trying to identify their gender while they are chicks or pullets/cockerels. If you're worried you've got some roosters in the mix, treat all the chicks as though they will mature...
Very possible and actually very enjoyable to have a bachelor group. But do so while they are young and not interested in the hens instead of waiting until after they have reached puberty. This will greatly lessen frustration by having "their hens" taken away. Also, just keep an eye on them. I've...
I give my hens and roosters anything they want. If they turn their beaks up at it, so be it. If not I let them chow down. I see no reason not to give them mealworms. I treat my birds with them on occasion, especially if I need them to go back in their run!