can i do an avatar/memoji on my iPad mini

The other reasons.

Memoji and Animoji Stickers, for iPads that can run iPadOS, requires an iPad that has an A9 CPU or greater. The iPad Air 2 and iPad Mini 4 models ONLY have A8X and A8 CPUs, respectively, and are ineligible from getting the Memoji Sticker feature of iPadOS.

For very good, third party Memoji apps for yout iPad model, I recommend either Emoji Me or Your Avatar Creator.

Good Luck to You

No, sorry. That's possible on iPhones and/or iPads using Face ID:--> iPhone and iPad models that support Face ID - Apple Support

Regards

Giulio

You are welcome