Or one could say "Cá bhfuil an t-óstán a bhfuil tú ag fanacht ann?" to distinguish this from "Where is the hotel that you own?" Come to think of it, the English is also ambiguous.
Should óstlann be acceptable here for hotel? Or is there a difference between óstlann and óstán?
It's given in dictionaries so I don't see why it should not be accepted.
I'm curious, for what reason cant I use "do óstán" instead of what it says is correct "d'óstán"
Even though d'óstán is really do óstán it is the practice to write d' for do before a vowel and before f followed by a vowel.
See number 1 in the list here.