Is execution flow of any executable file such as "WHATSAPP" in encrypted form? Can I make a timer which triggers "WHATSAPP" to send message to my "X" contact at "Y" time.
There are unofficial whatsapp clients you can make use of such as https://github.com/davidgfnet/whatsapp-purple or https://github.com/mgp25/Chat-API a PHP Library.
They're not reliable as whatsapp changes often specially introducing encryption recently.