My understanding is that you need to use the SD card in order to the firmware upgrade. Cool-ers website has a nice video on how to do it.
If go directly to the FW directory you can find the older version of the firmware.
http://www.coolreaders.com/downloads/fw/
I believe 1.12.6 was the file that was loaded in August.
I do understand that the later version of firmware released is faster though it doesn't open to the last book you were on.
Amy