how to know if the mobile is new or refurbished

1. Open the “Settings” app on the iPhone
2. Go to “General” and then go to “About”
3. Look for “Model” and then read the model identifier next to that text, it will look something like “MN572LL/A”, the first character will let you know if the device is new, refurbished, replacement, or personalized:

• • M – Retail / Brand new device, meaning the device was purchased new
  • F – Refurbished device, meaning the device has been through refurbishing process
  • N – Replacement device, meaning the originally bought device was replaced by this model likely due to a service request
  • P – Personalized device with engraving, meaning the device was customized with an engraving on purchase

Identify your iPhone model - Apple Support

https://support.apple.com/en-in/HT201296

If it was replaced by Apple, the N is correct as it is a replacement for another device.

N – Replacement device, meaning the originally bought device was replaced by this model likely due to a service request

Settings->General->About->Model

If the Model number starts with an M its new or at least not refurbished by Apple, if it starts with an F its refurbished by Apple.