I took the wallet.dat files and priv key when wallet isnt synchronized, its still %70 and loading, can I use this wallet.dat files later? or I have to wait full synchronized and take a backup files when it is finish. Im not sure about these .dat files.
No, you don't need to wait. Wallet.dat file will always contain your private keys and that is all you need. If you wait for it to finish syncing, the wallet file will contain the transactions for those addresses as well, but they are not necessary, as they are on the blockchain anyway and can always get them later.
Well said, and the difference between a backup wallet.dat file is it is more easier corruptible than a string of text being the public / priv keys of your bitcoin wallet, or printed out paper wallet. If that makes sense.