I cannot achieve some of the requirements for achievements due to having completed them on another version ie. console or pc. This one is specific to challenges. Also is there a controller input or accessory to make the controlling easier on Windows Phone 8?
Having the same problem too. Would really appreciate some help. Though I have read through some posts to find a possible solution: completing a Weekly Challenge/Manually having to count and complete an already completed challenge on any mission. Will try that soon enough