Chosen Solution

how to do a factory reset

The key combo depends on the manufacturer of the device as their are slight differences between differences between brands. The most common is pressing and holding the volume up + the power button at the same time. Another alternative is holding the Home + Volume Up + Power. Then in the case of something like the LG G2, G3 AND G4 pressing and holding the Volume Down + Power button is what works. What device do you have?

No volume rocker on the tab any new tricks

Seems like you added it a while ago .. did you solve this problem if so please contact me