I'm a beginner in RE. So i don't know which environments are better for me ( Linux or Window , 32bit or 64bit ).Which free tools are the best for each OS .Ollydbg is for Windows 32bit right?
Which environment are comfortable for RE ( Free tool )
windows;linux
There isn't really a better environment or best tools, its all up to the RE tasks you are up against. Since you said you are a beginner and from reading between the lines without a pre determined task, I would recommend 32bit machine and Ollydbg focusing on solving some CrackMe challenges.You can find some of them here:Tuts4You -  CrackMe