Back to V1.8.6:
No, Full-screen is not available. (only if the game resolution is any of standard 4:3)
I think there is a mistake here.
You say that "If the game resolution is not directly supported, backup resolution is used instead"
This is not true. The video card supports that resolution(as it does with 1440X900, 1680X1050 .....)
To show this I changed game resolution to 1440X900 and I had exactly the same results (and the same log)
The LCD monitor is the one that does not support that resolution, not the video card.
(in this case, it is a 22'' that works in 1680X1050),
So may be you should check the LCD monitor's resolution.
To my opinion,
May be the way of getting the "backup resolution" is not OK.
I mean, it ends up (in this case) to 1600X900, which is : 1600 is one step before 1680, and 900 is one step before 1050.
I think it should check for pairs (not independent X,Y) and only pairs:
That is (starting from game resolution 1280X800):
pair1= 1440X900, pair2= 1680X1050
Anyway there are not so many combinations
Usually these are 1280X800, 1440X900, 1680X1050, 1920X1200 (for wide screen)
May be I am making a mistake here, but I can't understand why this is happening.
I should expect that with some setting, the game to be stretched to the desktop resolution, displaying in full screen.
And the problem is that I can't go on if I can't have the game run in full screen.
Spyros