How to Use if Clauses in Your Mind

The first one is present tense and future tense. If I study, I will do well, I will pass the exam. The second one is for a condition in theory to be possible still to fulfill but we're using past tense now. And then the third one is where we're thinking about an event that is definitely in the past,. So none of it is changeable. Get out there and use if clauses all the time. Rocha also wanted to know, when do we not use if?