You have a training room.

This is a magical subspace. Time will stop while you are inside.

You can enter at any time. You cannot leave until you master a skill at the highest level possible for mortals

The room will magically preserve and passively improve your physical and mental health

You will also passively heal while inside. Disabilities will be cured

You will not age. It will manifest everything you need to train a selected skill.

You can Share this power with 3 people. You can only share it once. You can take it away, but never give again.

(Omniscience and godhood are not things that can be trained.)