What's your question? Ask

If I knew the answer, I would not have asked you the question.

It would have been best to leave it unwatered for the most part. The only thing that you can do is wait for new growth to return if is still alive. If after a few months you don't see anything, then it would have to be assumed that it is dead. You will know the dead from the living parts, as the live growth will be flexible. The dead growth will be brittle.

Usually, you will not have to do this. You can prune dead growth out, or prune to take cuttings, but this is not necessary for its health. I would do this during the time that it is not actively growing or after the flowers fade.

Here is an article for more information on this plant: https://www.gardeningknowhow.com/ornamental/flowers/desert-rose/caring-for-desert-rose-plants.htm

It is best to wait until the plant stops flowering. Winter when the plant is not actively growing will be the best time. Or anytime after flowering is also safe. Just use clean shears, and cut to your preferred shape. You may want to dab the cut with peroxide to keep it from getting infected, once every day for a week or so.

This article will give you more information on the care of these: https://www.gardeningknowhow.com/ornamental/flowers/desert-rose/caring-for-desert-rose-plants.htm

No this is completely normal for this to go into a semi dormant state. This is typical when they are far outside of their natural climate. When it warms back up, this will recover just fine.

You can bend the tip just enough to see if it is brittle, or still has some life. If it seems bendable, then you can scratch the bark with your fingernail just enough to see if there is still green underneath. This will indicate that it is still alive. It will likely recover if it is.

This article will give you more information on their care: https://www.gardeningknowhow.com/ornamental/flowers/desert-rose/caring-for-desert-rose-plants.htm