You can change the playback speed of the live classes only. 
Also, please be informed that you cannot change the video quality of a class. 

To change the playback speed of a live class recording on the Unacademy web:

1. Open the recording of a live class.

2. Hover on the bottom pane, and click on the Settings button.

3. Select the Playback speed option.

4. You can now change the playback speed by choosing your preferred option.

To change the playback speed of live class recording on the Unacademy Learner App:

1. Open the recording of a live class.

2. On the right vertical tab, tap on the Settings icon.

3. From here, you can select your preferred playback speed option.