Noun class. Ki/Vi nouns take changu in the singular (chake, chako, etc.) and vyangu in plural (vyake, vyako, etc.) Yangu (yake, yako, etc.) is used for M/Mi and Ji/Ma in the plural and N/N in the singular.

I think it could be either, just like the English sentence is ambiguous.

Nothing in the sentence equates to "all", so it is unnecessary to include it in the English sentence.

They have the same meaning in English.