(4/6) Tai Chi Basic Steps for Beginners: Rooting & Balance, Stepping Forward 

You are turning the foot by rotating the leg at the hip joint to avoid twisting the knee, but you want to keep your hips facing mostly forward although a little turning from side to is natural and not a problem.

Yes, you never want to lock the rooted leg. Always keep a slight bend in the rooted leg. It allows you to adjust your structure more easily if you start to lose your balance and it is safer for the knee. Happy training!

Thank you so much! Very helpful.

You're very welcome. :)

For increased stability (same reason you would have the foot of the rooted leg angled in a false stance or rooster stands on one leg stance). Granted, there are people that teach that you want to keep the foot straight and if you find that works better for you, then I'd encourage you to do it that way. Also, you want to make sure you keep your knee and toes pointing in the same direction. So, you wouldn't want the foot of the rooted leg to be angled while your twisting your knee to point it straight forward. Always keep them aligned and avoid twisting the knee. ;) Thanks for the question!