Saved -2009- Ok.ru -

Possible challenges include ensuring the accuracy of dates and features. I should cross-reference multiple sources to confirm when certain features were added. For example, Odnoklassniki introduced a mobile version in 2009, which could be a key point. Additionally, it's worth noting that Odnoklassniki is owned by Mail.Ru Group, which might have started incorporating it into their suite of services around that time.