As far as I know, there is no Pie firmware for any S912, AML has not yet released a workable SDK from what I understand.
If I recall you have a Mac PC. Do you recall what we did last time to get around not having a Linux or Windows PC?
VIM2 Android firmware can be found here.
Directions for flashing firmware can be found here, and here. How to enter in to update mode can be found here.
A new way to flash the VIM2 has become available, Krescue, though still in the experimental phase. A Krescue video how-to can be seen here.