Opera recently updated their Opera Mobile browser with the webkit powered engine. It replaced the older version which used Presto as the rendering engine.
The new Opera Mobile is an excellent browser no doubt but it performs poorly on devices with less processor power.
A lot of users of Opera Mobile were annoyed by the move and the company has listened to their complaints.
The company has brought back the presto version of the Opera Mobile. It is now available as Opera Mobile Classic from the Google Play Store.
It is not clear if Opera would continue to develop this older version considering they have already decided to stop development on Presto to focus entirely on Blink rendering engine.