@AnkujJ44 please can you specify what exact version of Pega you are running?
Note that there were some known issues with Page compare for page groups which were resolved in patches 8.7, 8.6.3 and 8.5.6 (BUG-665698, BUG-677527 and BUG-678908)
Field level auditing on embedded properties sporadically did not report the "old" value when a property was modified even though the page was listed as "Modified". This has been resolved by adding logic to the pxComparePages algorithm to treat Lists and Groups differently. Now Page and Value Groups will use pxSubscript as the primary way to detect add and deletes.
With regards to general improvement of the functionality, I have added the reference ID of the enhancement request that is in the system.
If you wish to discuss this with any Pega Account Executive, please quote FDBK-82606/ US-442635 (Enhance Field Level Auditing For Pagelists). The more users who quote that enhancement, the higher up the list of priorities it will go.