HT2519: Download past purchasesLearn about Download past purchases
Currently Being ModeratedMay 2, 2013 2:13 PM (in response to AndyTheAnimal)
To address your first concern, certain content may not be compatible with iTunes Match. The following article has more information (in the Additional Information section):
Also, regarding the issue of not being able to play unless connected to WiFi, I found the following information:
By default, when adding an iOS device to iTunes Match, downloading over a cellular network is not enabled*. To enable downloading over cellular for iTunes Match, choose Settings > iTunes & App Stores > Use Cellular Data > On.
*Fees may be associated with downloading over cellular networks; contact your wireless carrier for details.