Questions (interrogatives) in Quenya can be indicated by intonation alone, just like in English: túlalye? “you are coming?” However, more often they are marked with the interrogative particle ma. This particle was derived from the ancient root √MA, which was mentioned in several places (PE17/68, 162; VT47/19). Tolkien discussed its use in some detail in Late Notes on Verb Structure (LVS) from 1969:
Just as an interesting aside, a user over on TheTolkien Forum has shared his vision how Tom Bombadil's native language would've looked like. Here is the link: https://www.thetolkienforum.com/threads/bombadillo-an-ancient-language-whose-words-are-mainly-those-of-wonder-and-delight.28916/#post-532604
The subjunctive mood is used for various “unreal” (conditional or hypothetical) statements: things where the speaker is uncertain whether or not they are true. These are slightly different from the optative (things the speaker hopes or wishes were true) and the imperative (actions the speaker demands be done).
It's funny how things that should be evident sometimes stay hidden despite glaring in your face - yesterday I was musing about how I would express the adjective neutral in NeoQuenya. This, of course, led me to Etymonline and the aforementioned into-face-glaring, when I realized that L neuter, the basis of the word neutralis, is cognate of English neither, which of course makes all the sense in the world (Hungarian semleges "neutral" also comes from sem "nor, neither".
An optative is the expression of a wish, and Quenya usually formulates such expressions using the adverb nai “may it be that, be it that, maybe”. Its most famous use is in nai hiruvalye Valimar, nai elye hiruva “maybe thou shalt find Valimar, maybe even thou shalt find it” in the Namárië poem (LotR/378). Tolkien described this formulation in several places: