How to differentiate the Standard App and Custom App using "App launcher" or "App Manager"

Hello @Surya Sai Kiran you can use this tooling API query to get the list of all standard and custom CustomApplication from within your Salesforce instance. You may look at the standard NamespacePrefix

SELECT Id,Label,DeveloperName, Description, NamespacePrefix, NavType, ManageableState
from CustomApplication 

Eric