The Root Cause is that the new strings are missing from the custom locale files.
1) Compare and merge contents from USM_HOME\view\webapps\usm\locale\icusen\request\request_edit.xml to USM_HOME\filestore\custom\locale\icusen\request\request_edit.xml
(same has to be done in other locales, "icusen" is a folder for English locale)
2) If we want to update the confirmation message, we can do so by modifying the "<request_updated>" tag content in request_edit.xml file.
3) Uncomment the line we have commented during the webex to remove the alert, in USM_HOME\view\webapps\usm\explorer\scripts\widgets\request-edit.js -> showUpdateAlert(), to get back the confirmation alert.
Note: 1) Do compare all the custom files with the product files and merge the content into custom files to avoid any unwanted behaviour whenever a patch/rollup is installed.
2) No restart of catalog service is required but browser cache should be cleared to get the new changes into effect for any JS file modification.