I was reading Wallace on prepositions in his Greek Grammar Beyond the Basics and noticed how he deferred the reader to BAGD for more detailed lexical meaning. Other various books, articles, and linguistic resources I’ve seen seem also to defer to BAGD. The lexicon looks to be the standard.

Over the next few months I will be interacting with the LXX. I have found Rahlf’s edition to be the widest available text.

I say the above to ask three questions: 1) What other lexical authorities do you prefer or think is comparable to (or even better than) BAGD; 2) Does LXX Greek differ considerably from Koine Greek, and if so, what resources are available for helping one already familiar with Koine bridge the gap; and 3) Is Rahlf’s text the standard LXX text in biblical studies and what lexicon(s) would be sufficient for interacting with the text?