How old is my phone? And i want to know when i first used

Another method:

You can do so - with a bit of speadsheet manipulation - after logging-in at https://privacy.apple.com/

Download all of your data. (you’ll receive several CSVs)

Sort thru the files and you will find a one showing the date and time all of your devices were first connected to your AppleID.

Find you phone’s MAC and you’ll have your date.

If you have not...

• Changed your Carrier or SIM
• Reset your Device.
• Reset Statistics on your Device

The the Last Reset Date is when you first Activated your iPhone. Watch the Pic below