Answer-How many boxes are between U and R?

Only five boxes are placed between M and O. Q is placed immediate above O. Only three boxes are placed between Q and P. Following 5 cases are possible Number of boxes placed between M and P is same as between N and Q. Not less than four boxes are placed between Q and R. One box is placed between R and S. Box U is placed above box T. All the cases except Case3 eliminate as they do not satisfy the third hint. Thus the final arrangement is as follows