How to determine Plesk version/build?

Check this out : http://kb.odin.com/en/8732

How to find Plesk version in GUI?

Plesk version and microupdate information can be found on the Home page.

1. Login to your Plesk
2. Open Home tab. Under the System Overview section you will find panel version:

How to find Plesk version through command line?

Plesk for Linux

1. Version information can be found in the "$PRODUCT_ROOT_D/version" file, e.g.:

   # cat /usr/local/psa/version
   11.5.30 CentOS 6 115131204.15
   

   Output shows the Plesk version, operating system, and build number. In this example, the version is 11.5.30. The operating system is CentOS 6, and the build number is 115131204.15.
2. The following command shows information about installed microupdate:

   # cat /root/.autoinstaller/microupdates.xml
   <?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
   <patches>
       <product id="plesk" version="11.5.30" installed-at="20130925T023056">
           <patch version="29" timestamp="" installed-at="20140118T033218" />
       </product>
   </patches>
   

   In this example, Plesk version is 11.5.30. The microupdate version is #29, and the date when it was installed is2014/01/18 at 03:32:18.
3. Also you may use system package managers to find your Plesk version:
   RPM based system:

   ~# rpm -q psa
   psa-11.5.30-cos6.build115130819.13.x86_64
   

   on Debian:

   ~# dpkg -l psa
   ii  psa 11.5.30-debian6.0.build115130819.13          Parallels Panel v11.5.30 core files