JB possibility depends on the firmware version. The upper jailbreakable versions are
PW2: 5.8.7.0.1
PW3: 5.9.6.1
PW4: 5.10.1.3
KT2: 5.8.7.0.1
KT3: 5.8.7.0.1
KT4: 5.11.0
KV: 5.8.7.0.1
KOA: 5.8.7.0.1
KOA2: 5.9.0.6
Especially for PW4 look here
https://www.mobileread.com/forums/sh...&postcount=724