1) Clothes is plural noun means a single dress. Singular ‘clothe’ is used as verb to express covering of the body by clothes. So you can say: 'a pair of clothes’ or 14 pairs of clothes.
2) No, Clothes mean a single item of dress. ’Take off the clothes’ means remove whatever you are wearing.
3) Yes, Clothes and glasses(used for viewing or as spectacle) are plural nouns.
4) No, it can be a single item of dress or more than one item.
You go to a clothes shop for buying dress, a clothe shop is incorrect..