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This is a sign of too little water. Water the plant when the top of the soil is dry but don't let it dry out all the way through.

If the roots weren't damaged, the plant can regrow. Best thing is to wait and see if the cane sprouts new growth. This article will tell you more about saving freeze damaged plants: https://www.gardeningknowhow.com/plant-problems/environmental/tips-for-saving-cold-damaged-plants.htm

Wow! You have done very well. According to Wikepedia, they are native to Africa, and grow up to 49' tall. They're used sometimes for hedges and living fences. I couldn't find any information on lifespan, but considering that all you have to do to start a new plant is to stick a piece of a cane into the ground, I'd say they're pretty close to immortal.

If you want to remove the plant, I would recommend digging up as much of the root system as possible to ensure that it does not regrow. You can treat the area with Roundup but keep in mind that you will need to let the soil sit for 1-2 weeks to let the Roundup break down so that it does not kill any new plants you put in the soil.

Transplanting any plant is basically always the same: select the proper site in terms of light, amend soil if necessary, dig up plant transporting as much soil as possible, and water well for the first couple of months (adjusting water according to plant, soil, and climate.) Janet craigs are going to do well in shade or light shade. You probably don't want to put them where sun will hit them directly. This article has more information on transplanting: https://www.gardeningknowhow.com/plant-problems/environmental/learn-how-to-avoid-and-repair-transplant-shock-in-plants.htm

No, Massangeana is not going to get cyclamen mite. It looks like it might be getting ready to flower.