boot2v2 was the version of boot2 installed on RVL-CPU-01 consoles. While it was never released on NUS, many early discs had it in the update partition, removing most traces of boot2v1.
boot2v2 is not very common anymore, because the 4.2 update caused all consoles to update to boot2v4.
boot2v2 has the same IOSP build date as IOS9v516 (September 1, 2006), possibly indicating that it was built in a similar hurry as IOS9. The exact changes from boot2v1 are not yet known.