[RPG] Languages and Knowledges

[Ki] is an element of the magic that suffuses the multiverse—specifically, the element that flows through living bodies. (PHB 76)

In the context of the above statement, we should understand the term "spoken" in the Tongue of the Sun and Moon ability description to mean "sound created by a living being". This is reinforced by the claim that the monk learns to "touch the ki of other minds".

1. The monk communicates and receives these meanings by a sort of mental bridge between herself and the other creature. The speech is also occurring for the monk, but she has no automatic comprehension of it. This is also supported by the fact that written language is excluded; a piece of writing has no present mind to communicate it to the monk, and so she cannot read it.
2. No. A recorded audio message suffers from the same limitation as a written message: it is mindless.
3. No. The understanding is conveyed by the monk herself, and if she leaves, then the message is mindless. The spell Magic Mouth requires the monk to "speak the message". The monk is incapable of speaking the message in other languages, and as the spell is not a creature, it cannot understand the mind-speak that the monk uses to communicate to other creatures.

Languages don't come from stats, ability scores, or skills. They come from race, and possibly from class or background.

Languages

By virtue of your race, your character can speak, read, and write certain languages. (PHB p.17)

From their first mention languages are set out as a racial benefit. Two exceptions arise--Druidic and Thieves' Cant--as class benefits. Later, we see that knowledge of a language may arise from a background (p.125) or from extensive training (p.187). Which gets us to my interpretation:

Languages are part of your deep background.

Language acquisition as a racial feature arises from assumptions about segregated communities; the DMG (pp.20-21) discusses ways in which one might adjust these assumptions and how that might impact language acquisition. (They give the example of a racially-blind kingdom-dependent language system as an alternative.)

Language acquisition as a class or background feature is more-explicitly based on long times spent in the relevant community/diverse settings/life of study. Note the acolyte and sage gain two languages; guild artisan, hermit, noble, outlander each gain one. Alternately, you can pay to train for 250 days and 250 GP. This also constitutes a large amount of time, effort, and investment on the part of the character.

Thus, changing your ability scores, statistics, or skills have no effect on your languages. Because those changes haven't changed your experience, by which you acquired language. (Admittedly, those changes might impact your ability to hear, speak, read and/or write, however.)

Languages aren't a skill. They aren't tied to an ability modifier and your broficiency bonus in that way because they're binary: you can't (RAW) be more- or less-skilled in a language.

Languages aren't pegged to attributes. But they used to be. Originally PCs were guaranteed two languages: common and alignment. INT>10 made it possible to know more languages. In 1e your intelligence capped the number of languages beyond your base (racial/class) languages that you could know. In 2e your intelligence capped the total number of languages that you could know, all the way down to INT=1 capping you at zero languages: "while unable to speak a language, the character can still communicate by grunts and gestures." (PHB1e p.10, PHB2e p.16)

[ed.: I'm working off of retroclone material for the Original cite: if anyone's got a good cite to edit in I'd appreciate it.]

Is it related to personality? Personality isn't really a defined term in D&D, so this gets sticky, fast. For our intents I think it's easy enough to say "no," but recognize that language and personality formation are interwoven in real life in a way our game just isn't trying to simulate.