You have just clarified something for me. If the demonstrative is being used as an adjective, eg this hotel...then you need the definite article: so, 'ez a szálloda...', but if it's being used as a pronoun, eg this...hotel then you don't: so, 'ez....szálloda'. Köszönöm szépen.
This is a good question that I would love some igazi magyar insight into. I know that oreg is more often than not used for people. For instance an oreg harcos is a veteran (might answer your question, though I'm sure hungarian probably has a way to do the ex- as well; however, that being said, regi is occasionally used for people as well, such as regi baratom (my old friend).
- Also looking in my dictionary it looks like "volt" (past tense to be "lenni") is often used for ex- volt ferj (ex-husband) volt elnok (ex-president)
You are right, "volt" is often used to express the english "ex-", it works similarly. As for the difference between "régi" and "öreg" they are used in specific cases (e.g. öreg for people and animals and régi for lifeless things), but they are interchangeable to a degree (you could say "öreg autó"). Also "régi" implies that something is old, but does not say anything about its "condition" ("régi autó" simply means that it's old, but "öreg autó" kind of implies that it is aged or has been used a lot during its lifetime). Sorry if I overcomplicated things, it's kind of difficult to explain these small differences. Also "régi" pretty much means "something from long ago", and that's why it can be used for "régi barátom" meaning "my friend from long ago." However it cannot be used for people like in "régi ember".