Imprint and a privacy policy?

I want to open a website where I offer my Minecraft plugins, texture packs and maps for free download. Now my question is do I need an imprint and a privacy policy?

Yes you do.

Is there an exact age before you can create an imprint?

There are minimum age and form requirements for commercial activity.

An imprint is due very quickly. If it is missing, there are expensive and annoying warnings.

On the other hand, it is extremely unlikely that you will get in trouble because of being "too young" just because a website is operated with an imprint.