Yes, you can have this 10% scan and pay offer multiple times even for the same merchant.
Other offers like Ola money wallet addition 10% cashback (upto ₹250) using promo code 'Taxi' is limited to once per PayZapp wallet/Ola/one time.
You will be asked to put OTP received in your PayZapp linked mobile number. Provide that and you'll logged in even if you don't have the number in your phone.