If you want to bring your travel forward, you could but only on 13 Dec, there are some seats on EK418 in F, Y/W, and a couple Y on EK412.


As for later dates:
23 Dec, only 1 seat in F on EK412
24 Dec, few seats in F on EK418
25 Dec, 1 seat in F, couple J/C on EK412

As far as using your miles, if your booking was on EK412, you could do so but only on the 25th.

That's all I could think of, hope it helps.