Can i get Eevee before beating Elite Four?

I searched on the internet and found that some people say we can receive the National Dex before the Elite Four, while others argue that it is necessary to become the Champion to receive the National Dex.

The first question is: Can I receive the National Dex before beating the Elite Four?

To get Eevee, we need to have the National Dex and receive Eevee from Bebe.

The second question is: Can I get Eevee before beating the Elite Four?