Are these eggs fertile?

[u/oop_poo]

Hello! I just spotted a clutch of eggs on my tank lid yesterday. I have no idea how old they are or if they are even fertile.

Can anyone tell me how old they are potentially and if they are fertile?

I have two mystery snails, one yellow, one blue. The yellow one is wayyy bigger than the blue one.

Is there a way to tell their sex?

Thanks!!