Ancient Greek, especially in it's earliest forms (we can maybe even talk about Mycenaean Greek, although we don't have enough text from it for it to be a "complete" language), but Attic, especially "Homeric" Greek is very spiritual and holy.
Sanskrit is also in this category (Although we don't know what language did the Vedas wrote in, the texts are and newer versions of the original, like with many ancient texts), but one is just better learn ancient Greek because of the richer literature.
Latin is also very great, although ancient Greek is more perfect according to HPHC.
The other languages you mention (and generally other ancient languages) would not worth to learn that much, since they only have like 1-2 books or fragments of writings.
The language in Lemuria from which probably all of these languages evolved, that is probably the most Holiest language. The Indus valley script is probably the most direct descendant of the Lemuria language.