How to make column go reversibly blank with custom validation and conditional format rules

I was able to use scripts editor to make some conditional formatting. Would like the option of covering up the answer column, column B reversibly. Would love some help with a script or how to do this. Just learning how to program.

https://docs.google.com/spreadsheets/d/1kBTrLIxMBRcKB-Y2gJxPP_-_zihOc4xFTFrgDktZp-M/edit?usp=sharing