Open it with a hex editor; RAR4 starts with 52 61 72 21 1A 07 00 , while RAR5 starts with 52 61 72 21 1A 07 01 00 .
Run strings 186.rar | grep -i "flag" to see if the flag is visible in plaintext. 186.rar
Before diving into tools, verify the file's basic properties to determine the next steps. Open it with a hex editor; RAR4 starts