If you want to open your root chakra through mudra then there are two mudras that you should do, Shambhavi mudra and another one is Trataka mudra.
She is doing shambhavi mudra, she is looking in between her eye brows
She is doing Trataka mudra, she is looking at the flame of this candle
5 to 6 months
Yes, not only this mudra balance your root chakra but it also help to unblock it
early in the morning you should do Shambhavi mudra and at night you should do tratak mudra
No, this is the safest way to open your root chakra
Chose a very keep and quiet room to do this meditation. make sure no one is around you and no one disturbing you