i have connect my industrial AB PLC with node red installed on rbpi4 and sending data on whatsapp is connecting rbpi with wlan secure or using that whattsapp via node red is secure because i have added the unknown number that is provided by nodered to add api on whatsapp
Define "secure" in this case?
As long as Node-RED is only reaching out to WhatsApp and not recieving an unsolicited connection from it and as long as the outbound connection is using HTTPS then that aspect is reasonably secure.
As the number you have given isn't real, that should be OK
But if others can see and use the number, you need to make sure that you aren't letting people send information that you then process without sanitising it. With Telegram, you might limit inbound messages to specific user ids for example and then you would still sanitise the incoming data - so no excessive sizes, no weird characters, and definately no using inputs directly into database queries.
You can consider it secure, but your context and use case should set the security you need.
Can you describe the requirements you have?, if this is for a Lab / DIY scenario, you can use a shared number whatsapp relay, it's free and a reliable service.
This is the one I am using with some colleagues, should you want to give it a try: