No, you don't! The game is free and should be totally functional on its own - if 👌 you get a message telling you to purchase Modern Warfare 2 to have access to everything, that's actually a glitch, 👌 as listed on our Warzone 2 error codes page.

Yes. All Modern Warfare II attachments will be available in Modern Warfare 👌 III and can also be used on MWIII weapons, assuming they are attachable to the weapon in question.