Hi Javier,
I am copying my reply to the cstex list because I am not autoritative for Slovak and maybe I will not be precise enough. I am giving my commnents to Czech (cs.ini), Slovak (sk.ini), and Hindi (hi.ini). Some comments are common for all.
I do not understand the meaning of the encoding field. T1 and OT1 are font encodings for use with 8-bit TeX, XeTeX is able to use UTF-8 or UTF-16 and such fonts are available. IL2 (in Czech) was historically used in cslatex. It is preserved for legacy documents but deprecated, unsupported in babel and should be deleted. I know nothing about LY1. Before Unicode there existed many private encodings for Devanagari, many web pages used it and it was necessary to install a special font. Such fonts can still be found but IMO there is no sense to support them.
I understand hyphenchar (should be the same as in English in all mentioned languages) but do not understand the other hyphen* fields.
The minus sign in both Czech and Slovak should be –
The quotes in both Czech and Slovak are „ and “ (the closing quote has its codepoint in Unicode but is rarely present in fonts, it is better to use English opening quote which has the same shape).
In Czech (and maybe also in Slovak) the time separator is a period, in sport results and time tables a colon is used.
Slovak: characters Ä Ď Ô Ť in index look strange to me, it should be proved by a native Slovak speaker.
Hindi
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See the note on the encoding above
A few misprints and missing items in the captions
bib = संदर्भ-ग्रन्थ (or संदर्भ-ग्रंथ)
contents - the version you have is one of the alternatives suggested by Anshuman Pandey but most books I have bought in India contain अनुक्रम
part = खण्ड (or खंड)
page = पृष्ठ
proof = प्रमाण
glossary = शब्दार्थ सूची
cc, encl, and headto make no sense, I am probably the only man who writes business e-mails in Hindi...
I have never seen abreviated months (a native Hindi speaker should help). The only abbreviations for days of week I have seen at the Aligarh railway station are:
Monday = सो॰, Tuesday = मं॰, Wednesday = बु॰, Thursday = बृह॰, Friday = शुक॰ (or शुक्र॰, the plate was not clearly readable), Saturday = शनि॰, Sunday = रवि॰. I would not be surprized if the ॰ punctuation were omitted.