Is it possible to send message using the WhatsApp server to a WhatsApp group, inside my own application and without opening the WhatsApp app?
Also please help me regarding the history of WhatsApp contact chat.
in short NO
Reason: because (at least to my knowledge) Whatsapp does not allows the same. i.e. no external events or APIs to implement the same. So you have to at least use the intents and let the user handle the rest.
Also please help me regarding the history of WhatsApp contact chat.
This also can't be done (using ethical approach) because all the chat history is stored in a private database which is not revealed to the external apps by the Whatsapp application and also potentially violates the users privacy.