How to force a factory reset or hard reset on Symphony devices

Symphony V130 Symphony V130
Symphony P9+ Symphony P9+
Symphony P11 Symphony P11
Symphony i110 Symphony i110
Symphony Roar V78 Symphony Roar V78
Symphony i70 Symphony i70
Symphony i100 Symphony i100
Symphony Roar V150 Symphony Roar V150
Symphony V150 Symphony V150
Symphony V92 Symphony V92
Symphony V96 Symphony V96
Symphony i75 Symphony i75
Symphony V44 Symphony V44
Symphony V140 Symphony V140
Symphony V135 Symphony V135
Symphony i15 Symphony i15
Symphony i120 Symphony i120
Symphony G100 Symphony G100
Symphony V98 Symphony V98
Symphony V145 Symphony V145