How to remove substitution/extension to a VO object in OAF

There are three ways, but firstly you must understand the basics of how Oracle stores OA Framework substitutions. When you load the substitutions using jpxImporter, Oracle creates a site level personalization, which gets stored in the database. Now to rollback/remove/disable viewobject substitutions
Option A. Delete personalization, using jdr_util.delete_documents
Alternately use "Functional Administrator" responsibility to delete the personalization
Option B. Disable personalization that corresponds to substitution, again using Functional Administrator
Option C. Set profile "Disable personalization" to Yes at site level

The common thing about all three options above is that they all pertain to removal of personalizations that were created as result of view object substitution in OA Framework.