This site has info on basically all the vintage Tamagotchis.
Before posting questions like this, I think it's a good idea to try and research it yourself if you have the time. For example, by just typing 'Osu and Mesu' into www.google.com, you can get a ton of information on the first page, way more than I could ever answer.
Also visit Mimitchi.com and check out Kat's logs, because the logs in particular have awesome information on osu/mesu. I am currently on generation 3 with my pair.