What reagents can be used to distinguish pentose and hexose sugars?
I'm not going to address all of the reagents, but I want to highlight a specific approach in this partial answer.

Occasionally, knowing some history of chemistry is quite useful when thinking about how to solve problems. In this specific case, I direct you to the work of Emil Fisher (chemistry Nobel 1902), who determined the structure of all hexose sugars. He did this by building up the sugars from smaller subunits while keeping track of symmetries.

This immediately suggests a solution where one performs reduction (or oxidation) of the aldehydes. In other words, make the both ends of each molecule look the same. This is a valid strategy because the underlying symmetries of glucose and xylose are different.

The penta-ol is meso and therefore achiral, while the hexa-ol is chiral and optically active since you started with one enantiomer.

Thus, any reagent that can produce the bis-acid or bis-aldehyde without epimerizing any stereocenters along the way or any reagent that can reduce the aldehyde to an alcohol will provide a suitable method of differentiation in this specific example.