Can I use "if" instead of "whether" here?
Unfortunately, you cannot use "if" in this sentence. If a sentence is conditional and only presents one option, it is usually okay to use "whether" and "if" interchangeably. However, if a conditional sentence presents two alternatives, you should always use "whether". Ex: I don't know if she's going to the party. Ex: He didn't say whether or not he is interested in the job. Ex: Whether rain or shine, we will still have the soccer game.