Devices with less than 1GB of RAM memory are more likely to have problems running Magpi, and more RAM may be needed for longer or more complex forms. WE DO NOT SUPPORT ANY DEVICES THAT DO NOT MEET THESE SPECIFICATIONS.
Also, never go to the field without testing your form on the same kind of device that will be used in the field, well in advance of your field activity. Longer forms require more memory, which usually means a more expensive phone, so do not plan to collect data with a 500 question survey on a $30 basic phone (or tablet). Performance of a particular form on a particular device cannot be determined without actual testing.