(...) It is unclear how the plural participle translated “knowing” is functioning. On the one hand, יֹדְעֵי (yodÿ’e) could be taken as a substantival participle functioning as a predicative adjective in the sentence. In this case one might translate: “You will be, like God himself, knowers of good and evil.” On the other hand, it could be taken as an attributive adjective modifying אֱלֹהִים (’elohim). In this case אֱלֹהִים has to be taken as a numerical plural referring to “gods,” “divine beings,” for if the one true God were the intended referent, a singular form of the participle would almost certainly appear as a modifier. Following this line of interpretation, one could translate, “You will be like divine beings who know good and evil.” The following context may favor this translation, for in 3:22 God says to an unidentified group, “Look, the man has become like one of us, knowing good and evil.” It is probable that God is addressing his heavenly court (see the note on the word “make” in 1:26), the members of which can be called “gods” or “divine beings” from the ancient Israelite perspective. (We know some of these beings as messengers or “angels.”) An examination of parallel constructions shows that a predicative understanding (“you will be, like God himself, knowers of good and evil,” cf. NIV, NRSV) is possible, but rare (see Gen 27:23, where “hairy” is predicative, complementing the verb “to be”). The statistical evidence strongly suggests that the participle is attributive, modifying “divine beings” (see Ps 31:12; Isa 1:30; 13:14; 16:2; 29:5; 58:11; Jer 14:9; 20:9; 23:9; 31:12; 48:41; 49:22; Hos 7:11; Amos 4:11). In all of these texts, where a comparative clause and accompanying adjective/participle follow a copulative (“to be”) verb, the adjective/participle is attributive after the noun in the comparative clause.
(Source: footnote 2tn appended to Genesis 3:5 NET)
In conclusion, here is the answer to the detailed questions.
- What is the correct translation ?
The translation given by NET is "... you [Adam and Eve] will be like divine beings who know good and evil"
- What textual justification is there for placing the emphasis on Adam and Eve's supposed 'knowledge' or upon God's supposed 'knowledge' ?
See a.q. footnote 2tn
- Is the concept of a 'plural construct' in Hebrew the same as a 'collective noun' in English ?
What we can say is that יֹדְעֵי (yodÿ’e) is definitely a plural participle. OTOH, אֱלֹהִים (’elohim) is the plural of אֱלוֹהַּ ('elowah - see Strong's H433). Referred to God Himself, the plural ’elohim agrees with a verb in the singular. Referred to "divine beings" the plural ’elohim works as a real plural, and agrees with a verb in the plural.