if I am trying to make a cool moves, do I have to play againts another player or just free play?

Both actually.

Single player can help you experiment and refine what you have learnt as well give you the time to get familular with controlling your Tori.

Multiplayer is good for testing the practicality of moves and can give way to sporadic awesomeness. (accidentally finding a very good move)

how about many replay that so popular? they use free play
-----
how is unibash are they have to be paid?

Unibash is free, you can sign up for ingame classes here: http://forum.toribash.com/forumdisplay.php?f=441
Just look for the area you want to be trained in, a lot of tutorials also found there can help you out as well.

Do you know whats clan is? There are official clan and unofficial clan there.

Yah clan are basicly a group of members that gather and talk and fight as a group but these clans also have requirements so make sure to read the first post

Now the diffrence between an officail clan and an unoffcail clan is that officail clan have passed the clan councils reqs to gain thier own board (along with an officail tag )

How about the ranks of all clan? Whats the rank in the clan meants?

It tell you how good the clans are based on how many clan wars theyve been in and won (which is tallied in pionts which you will find to the far right of each clan

Are clan must be an official clan in the end?

An offical clan is certainly better than an unofficial clan, but you don't have to be official if you don't want to/can't afford it.