An advanced English speaker might speak better than native English speakers,oh,it's a shame,but it's logically reasonable,isn't it?

I agree one's native language is the one you were brought up with. So this may include the language of your community as well as your home language, if they are different. What is misleading is to assume a "native speaker" is therefore a good speaker of the language. When one says "advanced knowledge", the level of quality is pretty clear. But in using "native speaker", perhaps we confuse "authenticity" with "quality". My point is, it is perfectly possible for a native speaker to be very poor at their own language, even illiterate. Which brings us to advertising for language teachers - naturally the employer requires a certain level of education, but would request and favour a native speaker (who may have to also LOOK like a native speaker) with less education and experience above an older, more researched and experienced teacher who is not "native". Seems unfair, but the "native speaker" request seems to be a shortcut which avoids the extra task of assessing each candidate in detail. All up, perhaps we're trying to compare apples and oranges. ;)

In my opinion a native speaker is a person who learned the language beginning as a baby / child in a community of people who speak it as a first language. The community could be his/her family, a town, a part of country where they use that language. It doesn't have to be the official language of that country. If they grow up using that language as their "daily" language, they are native it in as far as I'm concerned. They can communicate with everyone in that language automatically and correctly (with friends, officials, etc. ) A lot of people are lucky enough to have both of these, the language of their immediate community and the language of the country they grow up in. That must be a wonderful situation -- having more than one language and not having to do all of the work as a "second language student." Now I'll go memorize some Spanish irregular verbs since I'm not a native speaker. : )

Hi... A language is always in evolution so you need to be ready to adapt yourself to that evolution... but the most important thing is what you have in your heart about your language... A language is not just a communication tool, it is a lot more than that...including Culture, History, Religion, Art etc...

I doubt the existence of such a line. You are asking what the 'defining' line is between the two fuzzy concepts 'native' and 'advanced'. As a manner of fact, it'll be more smart of people trying not to figure out 'defining' definitions in linguistics. But we have to admit that it is so curious to study the babies who just begin to be able to listen, talk and understand.