30% means that there is no consistent reference, the system is dead, and only exactly the same content will be refreshed. If there is a reference here, it will be ignored. So, in your statement above,

1. Correct

2. Correct (but it is difficult to operate, because if there are too many sentences and too long paragraphs, I am afraid it will still be red)

3. You can quote 30% at most. I don't know who told you, but it certainly has nothing to do with duplicate checking. The reason why you can't quote too much should be the teacher's request. Graduation thesis requires innovation. What if they are all quoted?

4. impossible