A kitten will be considered a cat when it's nine months old. I once read that a cat was adolescent from about 10 to about 18 months of age... I guess that means s/he's an adult past 18 months of age.
Ethnically, Mexican Americans are a diverse population including Mexicans of Indigenous ancestry, Mexicans of European ancestry (mostly Spanish), and Mexicans of Middle Eastern stock (mainly Lebanese).
The main difference between Mexican and Hispanic is that Mexican is a nationality whereas Hispanic is an ethnonym. Mexicans are the natives or inhabitants of Mexico. Hispanics are the Spanish speaking people, especially those of Latin American descent, living in the United States.