1.posibility in caunterfeiting bitcoin, how real is it or unreal..
it is not possible to counterfeit bitcoins because bitcoins doesnt really exist. all you have is a private key (which is a very bug number) which works like a key and authorizies you to spent outputs you have received from other parties.
2. Does it have any legal protection from the laws and etc in real world?( copyrights, etc )
only protection is, that it is not allowed to circumvent security to get acces to a system. so probably the answer to your question is no.
personally i think this is good: bitcoin is about beeing your own bank. this means self-responsability. this starts with thats your own obligation to secure them
3. Can someone claim the rights about its invention?
no
4. After the last bitcoin is mined, if it happens, how much money do one person need to have to buy it all if it has value usd eur ?
its impossible to buy them all, because some are lost.
buying the available rest depends on its users

but i think its impossible..
5.Is it posible that someone can be so rich these days to buy them all?
see answer 4. but i still think no. why would somebody do this? if only one person holds all bitcoin they would be practically worthless.
6.IF someone comes up with saying i did it, proves it, can he claim all bitcoins as only one legal owner?
That is it i quess, if it sounds funny or whatever, pls just ignore it, I am new in this world
if someone really has bought all (very very unlikely) yes he is able to proof that.
as i said above: there are no coins you only have a private key. with this private key you can sign a message which proofs that the owner of said coins did wrote that message.