Hi there saagarcruz,
Thanks for using Apple Support Communities. It sounds like you have some questions about how FaceTime works when you have multiple devices set up. Your Apple devices will work together to try to deliver your FaceTime calls intelligently. If you are using your iPhone your iPhone will ring when you receive a FaceTime call. If your iPhone is turned off and you are using another device, like your Mac, you will get your FaceTime notifications on that device first. Your other devices will show a missed call.
If you never receive your FaceTime calls on your other devices, check your Screen Time settings for any restrictions. These articles might also help:
Use FaceTime on Mac
Use FaceTime with your iPhone, iPad, or iPod touch
We hope this helps!