Casio's graphic calculator is either too bad or too expensive. It's up to you. I don't recommend any. Some students bought it and now regret it.
3. University calculus should use a graphic calculator. You just need to look at AP's calculus BC. There are many questions above that need graphic calculators, and many other disciplines also use graphic calculators in many places. Moreover, some functions given to you are defined by parametric equations. You can't imagine what it looks like without a graphics machine, or you can't even imagine it like this.
It is too expensive to buy TI in Chinese mainland. When you go to Hong Kong to take the SAT 1, you might as well buy a TI calculator from a regular agent in Hong Kong, which is much cheaper. I only need 1250 Hong Kong dollars to buy TI89 titanium gold, which is more than 1000 RMB. You have to buy it in cash in Hong Kong dollars, so you have to ask the UnionPay bank there to withdraw money. There is no handling fee in the same bank as your card, otherwise some banks only need to change it, and the handling fee is HK$ 100.
Before the exam, you should use the graphic calculator, otherwise you might as well not use it.
6.TI89 titanium and calculators with CAS are too powerful to be used in some exams, but both AP and SAT2 can be used.
7. Have you ever heard of the math experiment? Mathematical experiments in universities are not solved by this graphic function, and some use Mathematica and the like.