The Wikipedia page about IPOs says this:
A company selling shares is never required to repay the capital to its public investors.
Does that mean that stocks bought on the stock market are somehow different than those that existed before? Do they have a different name, and if so what is their name and what's the name of the original stock? Can the pre-IPO stock be traded on the stock market?
Say that Bob has 10% of Acme's shares, and has had them from before the IPO. Acme might be required to repay the capital to Bob, right? Then he sells them on the stock market to Dan. Might the company now be required to repay the capital to Dan?