Lucky you, I received my PB360 Jan 28 and it had W101.15.1 version. The worse part is, I tried to locate your version but the PocketBook website still has the 15.1 on their site.
Regarding FBReader, I'm using v0.9.3, but I understand there's a newer version. The 9.3 you find it here:
https://www.mobileread.com/forums/sho...&postcount=174