Change the speed of games in Android / SpeedHack for Android Is there a way to slow down / speed up the actual game speed? For Windows PC, there is the Cheat Engine SpeedHack that does it nicely. Is there anything (requiring root or not) to achieve similar effect on Android?

Check the Cheat Engine wiki (linked above) for the description in the functionality.
Use GameGuardian. It perfect works on all Android versions include Lollipop and Marshmallow.

It have speedhack worked on arm and x86 devices, include x86 emulators like Bluestacks, Droid4X, Andy and others.