I downloaded the spotify app on my iPhone and I use it a lot.
It works great to me but I have one small issue. I made a large playlist through the years, but i can not sort it by date on the Spotify app. I'd like to start with my newest added songs. On the computer you can sort by date, length, artist etc. So why not on the iPhone?
There is a way to sort your playlist on mobile too. When you open your playlist pull down on it untill past the playlist image. There should be a little button with three horizontal lines on top right above the image. Press on that and the menu to sort the playlist will open.
There is more detailed explanation on sort and filter for all platforms here.