Pl see MOS Doc 443761.1 (How to check if a certain Patch was applied to Oracle Applications instance (11i or R12) ?). Go thru OAM and navigate to Applied Patches, or run a SQL query against AD_APPLIED_PATCHES.
how to find out applied patches in 11i instance for last two months ( only last two months) including timestamps information...please help
Query AD_BUGS table.
Useful Scripts for E-Business Suite Applications Analysts [ID 887438.1] -- 2. How to check if a patch is applied?
How to check if a patch has been applyed with adpatch [ID 472820.1]