Whether or If: 1. When both choices are given, we generally use whether rather than if: I don't know whether she's coming or not. (It would be possible to use if here, but less common.) 2. Before an infinitive with to we use whether: I don't know whether to accept their offer or not. (If would not be used here.) 3. We can use whether after a preposition: It's a question of whether we can agree on everything. (If would not be used here.) 4. Both whether and if can be used in indirect speech to introduce a yes/no question: Did they say whether/if they were going to be late? 5. After some verbs, we use whether: I doubt whether they'll make it. We discussed whether it was the correct decision. Generally, whether is considered more formal than if. Hope this helps :)

Yes, they are interchangeable in your sentences. No, you do not have to include 'or not' in the sentence with 'if' only if you use 'whether'.. Good questions! I don't care whether your car breaks down or not. I don't care if your car breaks down. I won't care if your car breaks down.

Whether ... or .... This is the form. If .... [then] .... [] means optional.

Sorry, I have typed a wrong word, in that example, "card" should be "car".