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jdk1811!
1) Yes, elite bonus does not count towards EQM.
2) Last flight is any that departs 12/31 11:59 departure local time or earlier. Ticket with flights split across the new year will count towards the year they departed, so your flight on 12/28 would earn in 2018 & 1/1 would be for 2019. Note that if you are doing this for requalification-- if your end of the year flights do not post by 1/1, it's possible for a status gap as status expires 1/1. Once they do post, your status will be restored.
3) AS doesn't offer a general buy-up/challenge. They may make targeted offers, but I would not plan on it. Usually you cannot call in & opt in to those targeted offers either.
4) Check out several of the following threads for ideas:
AS: 2016-2018 Consolidated Mileage/Status/Challenge Runs help needed
https://www.flyertalk.com/forum/alas...lp-needed.html