Apparenrly you don't know what for-ex reserves, and how they work, nor do you understand how economics works.Worst analysis I have seen on this forum.
China is sitting on trillions of cash. So no they don’t “need” cash. And oil contracts are negotiated for a period of time to smooth volatility.
Again use your brain, China importing oil from Iran will happen regardless of it needs cash or doesn’t (which it doesn’t). So 3B it receives from Iran would go right back out the door to pay for oil/gas from Iran/Qatar/Saudi Arabia.
Again use some critical thinking skills
As for oil pricing, when you barter, oil contracts get thrown out the window. China wouldn't be signing an oil contract with Iran over this, because it literally makes no sense to. Iran would essentially be using oil as a substitute for cash, so your reasoning gets thrown out the window.