The app is only for the iphone4
There are appanrently certain weeks (as a rough guide) where your baby will make big development leaps, a bit like the growth spurts in the early days (oh how I dont miss those). Theres one at about 47-49 weeks.
Ive had a look and apparently at this one they learn sequences. So they begin to realise that in order to complete a task you sometimes have to do things in order. The one after that is around 55 weeks.