Russian verb хотеться
1) Why is the verb in the neuter singular?
2) Suppose the non reflexive form хотело had been used. Would this change the meaning?
3) According to grammar tables, всем can be either neuter instrumental singular or dative plural. Which is it here and why?
The verb хотеться is a so-called impersonal verb, it is always used in the neuter form. It is alwazs reflexive. The verb хотеть is a personal verb, it is a different one. The verb хотеться is always used with the subject in the Dative case and the object in the Genitive case or an infinitive.
Мне хотелось хлеба. I wanted to eat some bread.
Ему не хотелось есть. He didn't want to eat.