Is it too late for God to shade me on the Day of Resurrection if I begin obeying Him after having committed many sins, and what should I do to be among those whom God shades?

The questioner can achieve the virtue of "a youth who grew up in the worship of Allah" by repenting, being righteous, striving for beneficial knowledge and good deeds, choosing good companionship, and being wary of bad companions. If he misses that, he can achieve it by fulfilling other characteristics, such as frequenting the mosque or loving one another for the sake of Allah.