I would think you have come to wrong forum to ask these questions. I don't know of many international typographers or TTF type designers on this forum. I would recommend you do a search for more typography-centric forums (maybe starting with http://www.typophile.com/forum/ and branching out from there.

However, I can say that the "Clear Format" button in Word does not kill an alphabet. Rather you are changing the typeface from whatever it was, to the typeface used by the Normal style. If you changed it back to the original typeface, the empty rectangles would return to the characters they were. This would tell you that the character set of the two typefaces cover different ranges.

And the base font of a document often depends on the document theme applied to it. Do document themes change when languages are changed in a document - I'm mono-lingual so it hasn't ever been something I have needed to consider.

__________________
Andrew Lockton
Chrysalis Design, Melbourne Australia