It prevents the cell membrane from breaking. also it gives it its rigid structure
It is the cytoplasm (which protects cell structures)
For this question I'm not too sure what you're asking because cells that transport water are basically xylem cells and these cells are hollow with nothing in them, and they transport water against gravity because of transpiration pull, capillary action and root pressure.
The cells that I know of with many mitochondria for transport would be the phloem so that the mitochondria can carry out cellular respiration to release energy for the translocation of sucrose.
When a frameshift mutation occurs, the string of DNA will be glued together. When this DNA is going to be part of a process, such as a transcription, whatever is causing the process is unaware of the mutation actually having happened.