Can the same phone number be registered on both the WABA (Vira) and WhatsApp Apps on phone?

No, a phone number active on the WABA (WhatsApp Business API) cannot be registered on WhatsApp Apps. If the number is currently registered on WhatsApp, you must delete the associated WhatsApp account before using it for the WABA (Vira). And, then further connect with Vira to utilize for automation and run campaigns on WhatsApp.