Apologies if answers to this are buried already in other threads. I couldn’t find any.

Have got the following booking:
Business Class on JL operated flights
One booking made with Iberia
Flight 1) LHR-TYO ticketed as IB codeshare
Flight 2) TYO-HEL ticketed as BA codeshare
2pax, one of them BA Gold.

Question 1
Attempted seat selection in JL website. For flight 1 a seat selection is not possible. I can specify a preference window/aisle but even that fails as website gives an error when trying to save choice.
Called JL, who advised to call IB to make selection. Called IB and they say I should call JL. Called BA Gold line, was told to call JL.
None of these airlines’ websites allows a seat selection either.
How do I go about selecting a seat?

Question 2
I am able to select seats on JL website for flight 2 but get error messages for the majority of seats I would like to pick. Seat map is wide open. Why do my seat choices get turned down?
Called JL to get help. What they were able to offer are seats 8A and 9A, ie at the very back of the cabin (not my preference) and seats that are behind each other, not ideal for 2pax travelling together. Agent on the phone simply said he can’t make other selection.
What dark powers are at play here that limit seat choices?