A young child is on all fours inside.
A youth is on hands and knees.
Young child and youth are synonymous. If you are on all fours then you must be on your hands and knees.
exists p1 s1 s2 x1.(a_inside(s2) & Manner(p1,s2) & all x2.(n_fours(x2) -> on(x1,x2)) & n_child(x1) & a_young(s1) & Theme(s1,x1))
exists p1 x1.(exists x2 x3 x4.(on(x1,x2) & n_knee(x4) & n_hand(x3) & subset_of(x4,x2) & subset_of(x3,x2)) & n_youth(x1))