Can you have 20 20 vision and still need glasses?

Yes: Glasses are used for many reasons: vision at distance, vision at near, double vision. Glare reduction, light reduction, etc. So you can have 20/20 vision (meaning good distance vision without glasses) and still need glasses for one of these other reasons.

Yes: You could have 20/20 for distance vision, but need reading glasses to see well up close (this is called presbyopia and happens to everyone starting in their forties).