Do you consider 'or not' as a kind of possibility? ('If' and 'Whether')
This question is about the words 'If' and 'Whether'.
I've searched on the internet and I know that you use the word 'Whether' when you have two or more possibilities.
But;
Do you consider 'or not' as a kind of possibility?
For example:
- I'd like to know if this sentence is correct or not.
- I'd like to know whether this sentence is correct or not.
Which one is correct?
Should I avoid using the word 'If' when I add 'or not' at the end of a sentence?
Example #2:
- I'd like to know if A is correct or B.
- I'd like to know whether A is correct or B.
Well, in this case, we have two options. A and B, and I guess the second sentence is correct. Is that right?
Thank you in advance.