Free Pro Upgrade if you can find 3 Love Letters in the App and share to 1 friend.
1. Heart booster (Toolbox, Heart Booster)
2. Homepage Edit (press the 3 lines in the top right corner (Android), then its 3rd from bottom.
3. Go to CPU cooler then once you have closed the apps down it will give u a summary....scroll to the bottom and it says read your love letters and tap read now and that's the third one. (Thanks to MikeyGolfGT)