Asterisk means that the word has been reverse engineered without any direct evidence backing it up. All proto languages will have asterisks in front of all their words because proto languages are, by definition, languages that were used before anything was written down.

The reverse engineered word is likely to be correct (or at least, as correct as we can be), but in the absence of direct evidence, it’s still just guesswork

The numbers you’re talking about are because we know that there are different consonants used, but we don’t entirely know what sounds those consonants are. So we just write all of the consonants that likely sounded somewhat like the letter h as h1, h2, h3, etc., and repeat for the other uncertain consonants.

So basically h1 definitely sounds different than h2, but as for exactly what they sound like, all we know is that both of them are kinda like h