Could: this means that you don’t know whether or not this person can actually help Would: this means that he/she can help, but may not want to Here is a simple way to remember: Would-Might if I choose to Could-Might if it is possible
It is incorrect to use “whether or not” with well-defined alternatives, such as “I don’t know whether or not I should go or stay” since this example introduces more possibilities than intended. The phrase “whether or not” is a condition, used in statements to show that something will or will not happen, regardless of certain
Jjust like you shouldn’t say “PDF format” or “ATM machine” because PDF stands for Portable Document Format and ATM stands for Automatic Teller Machine, please avoid “SPA application”. SPA after all stands for Single Page Application.