How to determine whether two hydrogen are homotopic, diastereotopic, emantiotopic?
You determine by labeling. Take the two hydrogens in question and label them one at a time to get two molecules. What's the relationship between these two molecules? If the molecules are the same, then the hydrogens were homotopic. If they are enantiomers, the hydrogens are enantiotopic. Otherwise, if they are diastereomeric molecules, the hydrogens are diastereomeric.