Since I've been given the go ahead to share source code for a game I wrote in AppGameKit, I don't think it will be to much to give you this.
Detecting a sprite hit by using a set of coordinates, whether you get those coordinates from the mouse position, a Touch event position, or the position of another sprite.
s is the sprite number hit. Returns 0 if no hit occurred.
In Tier 1:
s = GetSpriteHit(x, y)
In Tier 2:
s = agk::GetSpriteHit(x, y);
Not knowing a lot about C++ and namespaces, my guess is you can get that down to,
s = GetSpriteHit(x, y);
so there would be little to no difference between the tiers as far as syntax for the AppGameKit commands.