I'm buying an iPhone 7. How can I check that it's original phone? And it's intact?

ts.tanvirsolhel,

It depends on the seller. Is it an Apple store or other Authorized Reseller? If yes, you can assume it is new.

Otherwise, you might try to enter the serial number into the link below:

Check Your Service and Support Coverage

If the seller is an individual, make sure that they have released the phone as follows:

Turn off Find My iPhone Activation Lock

Good luck.

ts.tanvirsohel,

Based on the November 20, 2019 expiration date of the 1-year limited warranty, it would indicate that the phone was new and went into service on November 20, 2018.

Looks good to me 🙂