Been using it for a couple of weeks now, I like it but you can't upgrade on it unfortunately !
I have been able to download it now, creating a UAE Apple ID

You can upgrade with miles on the App.
You need to go to "My trips", manage your booking, then on the right top "..." -> manage booking -> "upgrade with miles".
On one of the flights where I am waitlisted for an upgrade to business I can only see the business seat map, but I am confirmed in economy and on the normal website I can only see the economy seat map. I cannot unfortunately choose a seat in business