Start11 is an entirely different product to Start10 so yes it is another purchase.
There is a discount for Start10 customers.
Start10 was designed for Windows 10 only which is why it does not work on Windows 11 as Microsoft made changes which stopped it from working. Start11 is designed for Windows 10 and 11 and comes with a significant number of new features as well as working on Win11.
Please note that references to piracy will get your account removed!