Great questions but the answers are not black and white. Basically you can grow that plant in a pot as small as about a half whiskey barrel for a very long time. I don't think repotting would be very stressful if you are careful with it and do the repotting in fall or late winter. I would go ahead and move it to the final pot size right away. If there is a reason to go to an intermediate size first then that is fine too.
That plant is very hardy and should do fine in any winter you have. If you want to be sure go ahead and move the container to a covered patio area on an unusually bitter cold night to keep the roots from getting so very cold. Water when soil is drying to the touch about 4 inches deep. Make sure container has drain holes and they are not plugged.
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