Find Unix Distribution Version

• cat /proc/version
• Linux version 4.14.219-164.354.amzn2.x86_64 (mockbuild@ip-10-0-1-103) (gcc version 7.3.1 20180712 (Red Hat 7.3.1-12) (GCC)) #1 SMP Mon Feb 22 21:18:39 UTC 2021 
• rpm -E %{rhel}
• 7

How to find java version of jar file

unzip test.jar
check for the file: 
META-INF/MANIFEST.MF (to get more details)

You see details like:
Created-By: 1.8.0_144 (Oracle Corporation)
Bundle-Version: 1.3.2.2