genders

Hello, I've been really interested in buying a cockatiel because of how gentle of a friend they can be. I was offered this one, the seller told me they don't know their gender, also added that they're around 6 months old. I really want a male cockatiel, I was told they're more likely to sing...

I have had this budgie since April of 2018, and his or her cere has never changed color. I figured that it's a she, but I wanted an expert's help, so I came here! I found it concerning her cere has never really changed color considering i've had her for almost two years. If someone could help...