Will Shi Gandang's handwriting turn in the wrong direction? Can it be removed and cleaned after long-term storage? Or can I just clean it on the spot? Thank you sincerely!

You can't change the placement position back and forth, as long as the words are not inward, there is no need to change.

Put it in its lost corner, and put it in the corner before nine o'clock in the morning.

So you just need to clean it up before 9 am. Don't touch it, just change direction. If there are other circumstances, you can ask the Feng Shui master to make a field survey.