Tier2 extension

Hi
i have to extend my tier2 visa and i have two questions, i would appreciate if any body can answer them.
1) do I need proof of English knowledge?
2) how long befor my currect tier2 visa expiration i should apply for extension( i prefer to apply at least 6 months in advance , am i allowed to do so?)
Thank you

1) For extension, no need to prove english knowledge and maintenance.
2) anytime before your tier 2 visa expires.