I understand that "quisiera" is considered the more polite way to make a request. But I was surprised when I checked my dictionary that this is an imperfect subjunctive. In English a polite request is "I would like..." and I thought that "would" usually translates in the conditional. So I have some questions about this usage.

Can you use querría for a request? "Querría un vaso de agua."

If I say "I would like" in the sense of a wish, like "I would like to go to Mexico some day", is that where I would use querría? So if I said "Quisiera algún día ir a Mexico" that sounds more like a request than a wish?

What about requests with other verbs? Subjunctive or conditional? For example, "¿Podría darme...?" or "¿Pudiera darme...?"

My dictionary says this tense of querer can be either quisiera, quisieras, etc, or quisiese, quisieses. ¿Por qué? ¿Son iguales?

Puede responder en inglés o español.