How each achievement for each app is earned is set by the developer of the app. Sometimes these change on a day-to-day basis.
With dozens of apps now supporting mPLUS Rewards, it's impossible for us to provide support for every type of achievement in all of our apps For this reason, the best and most up-to-date source for information about how to achieve things within a particular app is by contacting the app developers via their support channels or via their Google Play or iTunes page. Note: typically this link is found under the description of the app in the Play/iTunes store.
If that still doesn't help, please do feel free to submit a support request below, and we'll try to find out for you.