1.For TL-R470T+ V4
2.Old firmware’s configuration file can be imported into this new firmware.
3.Your device’s configuration won't be lost after upgrading, which means you needn't to configure your device again after upgrading.
4.It is necessary to upgrade the router to the middle firmware before upgrading to the latest one, more details can be found in the text file in the ZIP package.

Check the release note, submit a ticket if you do need a middle firmware according to the text file in the ZIP package.

http://www.tp-link.com/en/support-contact.html

There was a two bin do i need to update the tmp then the latest one?

Upgrade TL-R470T+_V4_tmp first and then upgrade the TL-R470T+_V4_141208 one. You can read Note.txt in firmware folder.

i was so scared because of this http://forum.tp-link.com/showthread.php?78870-TL-R470T-V4-firmware-upgrade-failed,
that why i ask first before i do =3. do the right thing.

Fully understand...:)
But no worries and follow the guide to upgrade. If it is still failed unfortunately, it is still under warranty. :)