1) The patchset level information can be retrieved directly via sqlplus with the following script :

Connect to the database via sqlplus as apps User
Review the adutconf.lst file.

2) Login to OAM

(Responsibility "Oracle Applications Manager", menu "OAM Support Cart")

and Navigate: Support Cart -> Applications Signature -> Collect -> Check "Product Information" box -> Click on "View" (eyeglasses)

This will display the following patchset information :

Application Name
Current Patch Level
Product Version
Status (Installed, Shared, Inactive)