Yes. However extreme flexion and extension poses can be hard on the spine so stay away form those types positions.
Perhaps. Yoga is a type of exercise that can increase strength, coordination and flexibility. When practiced within the limits of discomfort it may help give relief. Your personal response may vary. It is safe, and the risk is low, so give it a try if you are so inclined.
Several ways. It provides for flexibility and core strengthening and if done right, meditation to help with pain control. 90% of sciatic conditions due to disc herniations get better non operatively over time. Staying in shape helps to minimize recurrence and the severity and duration of any recurrence.