"When does it open?"
Translation:Il ouvre quand ?
In some contexts it will be equivalent, but the construct can just as well refer to "grand opening", or "working days", rather than "opening-hours" kind of opening. So you're limiting it a bit. I'd still accept the answer though. (but I'd rather see 'à quelle heure est-ce que ça ouvre?', actually)
no, or at least not without changing the meaning. You need to add an interrogative construct: "Quand est-ce que cela ouvre?" "Quand cela ouvre-t-il?" (which is a type of subject-verb inversion like in english interrogations).
"Quand cela ouvre?" corresponds to the English "When it opens?": you can imagine a colloquial context where making it a question works ("when can we get in the store? - When it opens? Duh!"), but the first instinct is to assume it is not a proper question.
"Il ouvre quand?" is translated as "When does it open?" also can be "Quand est-ce qu'il ouvre?" or "Quand ouvre-t-il?"
"est-il" means "is it?" You ask why not? Do you mean instead of "...est-ce qu'il..." ? This is a specific construction of French questions that cannot be changed. "Est-ce que" is used in many questions. "What is it?" "Qu'est-ce que c'est?"
Here is a site that explains French questions.: http://french.about.com/od/grammar/a/questions.htm
In formal questions, where the verb and the subject are inverted, you need to insert and pronounce a dummy "-t-" between hyphens to ease pronunciation.
This happens whenever the verb ends with a vowel (e or a) and the pronoun is "il, elle, on":
- que mange-t-il ? = what is he eating?
- quand ouvre-t-elle ? = when does it open?
- où va-t-on ? = where are we going?
that "l'" is a contraction of either "le" or "la", which I'm sure you know can be articles ("the"), or the 3rd person singular pronoun for direct objects. For subjects it's "il" or "elle".
Think of the difference in English between he/she and him/her
Your sentence is not grammatical because it doesn't have a subject, as it is.