To know if your WhatsApp web is active on an unknown device, go to the three dots given at the top right corner of your WhatsApp window. Go to WhatsApp Web and check the list of all open sessions. This will let you see all the devices that are connected to your WhatsApp.
When you call a dead phone does it ring?
Answer: A: With a dead battery it should not ring but it should go to voicemail directly.