https://wiki.openwrt.org/about/history
Openwrt Version:
12.09:
cat /etc/banner
ATTITUDE ADJUSTMENT (12.09, r36088)
uname -a
Linux OpenWrt 3.3.8
14.07:
cat /etc/banner
BARRIER BREAKER (14.07, r42625)
uname -a
Linux OpenWrt 3.10.49
15.05:
cat /etc/banner
CHAOS CALMER (15.05, r46767)
uname -a
Linux OpenWrt 3.18.20
Lede Version:
17.01:
cat /etc/banner
Reboot (17.01.1, r3316-7eb58cf109)
uname -a
Linux LEDE 4.4.61
Find out yours
uname -a
check match kernel version.