1) yes
2) no
3) It is good question but... submarines have different depth for other masts. Which mast is crucial for LADAR?
4) in very shallow water MPA/helo/SUBROC have big problem with dropping torpedoes. They crash to the bottom.
5) this is academic question. I think deploying SF without periscope sweep is not allowed because of procedures
688 H/K have described step by step procedures for SF operations