Sorry, this is a long question.

I have booked 2 tickets on SK with fare basis ZAUBIZSG, BNE-SIN-CPH-KEF return. Nice for me is that the long flights are on SQ. However codes allocated to the legs vary.

BNE-SIN is showing on the E-ticket as SQ236 (and on the SK web site, but initially booked as SK8008)
SIN-CPH is showing on the E-ticket as SK8000 (but flying on SQ352)
CPH-KEF is SK595

KEF-CPH is SK596
CPH-SIN is showing on the E-ticket as SK8001 (but flying on SQ351)
SIN-BNE is showing on the E-ticket as SQ265 (and on the SK web site, but initially booked as SK8009)

I am confused as to how to get best value, if any, out the the FF miles we can get. We both have plenty of FF accounts, but have sadly lost a few orphan miles over time. I would prefer to avoid that on these tickets.

We do not have Eurobonus accounts, but could open them if that seems best.

Before SK left Star it would probably have made sense to credit all legs to UA since we are both Lifetime Gold, UA miles don't expire, and have been of good value to us in the past. But now that SK is in SkyTeam it might be a different story.

Since the long hauls are on SQ, a Star carrier, can we credit the miles to UA on those sectors (and forget the short haul or credit them to a SkyTeam account)?

I cannot easily see how many miles we would be entitled to on each leg on these tickets. (Since SIN-CPH and vv is booked apparently with the SK code does that prevent crediting to UA for those legs?)

The only SkyTeam accounts with non-expired miles now is KE, valid to 2028. It might make sense to credit CPH-KEF to KE.

How easy is it to credit different sectors to different FF plans? Is that possible with SK. (I have had troubles in the past doing this with other airlines.) When I look in the SK website I only see UA FF nos, even though our E-tickets (which are agent badged) show our KE FF nos.

All a puzzle to me. Thanks if you read this far and are willing to comment.