Can someone explain the SpaceX IPO please

I am curious how this raises money and what happens to the stock when it goes live.

It is IPO’ing at $135 a share with 555,555,555 shares available, which all add up to the $75b Musk is looking to raise.

How does this get calculated exactly? Does everyone have to buy every share to hit that target? If all the shares were bought before the stock went live, does the price stay at $135 with no shares available, or does the price start to go up as the stock becomes more scarce?

What about private investors? Can they sell their stock the second the ticker goes live in the market?

Thanks for explaining