Re. D Class upgrade
From my experiences earlier this year you will have to wait until you get to DXB and then approach an Emirates desk and if there is availability upgrade
using your miles.
My Mrs tried at Birmingham enroute to Sydney & was told to ask at Dubai. If your Gold you may be wait listed for an upgrade? I rang a few days before departure, they told me they will add me to the wait list I checked my booking the next day & I had been upgraded.
All the best.
On another note it seem Skywards has changed for the worst after my partner had arrived back in sydney i checked her skywards account and she was only awarded 4500 tier miles & that was from BHX to SYD - This time last year we received over 11000!!!