I cannot recommend you buy this.
An M2 air is now two generations out of date. That could mean the battery has issues from non-use. A battery service in the US can be as much as US$200. No bargain there.
Also, the slightest feeling of discomfort with the provenance of any Apple device should have you running away. They are in high demand world-wide and fraudulent offerings are all too common.
Run. Caveat emptor!
I'd like to make sure that the Macbook is not stolen,
Apple does not have records of stolen devices. You would have to ask law enforcement to "run" the number through a national search system, like NCIS in the US. If they get a "hit" that shows it is stolen, they will confiscate the product on the spot.
Yes, checking the serial number on the Apple site may show when it was originally purchased but, sealed or not, you won't have a warranty on a device that stopped being a "new model" 18 months ago.
Please decline that device. We are happy to have you here but no one wants to find out that your were scammed.
Also see this:
The All Too Common SAD Reality of Buying … - Apple Community
It's about iPads and iPhones but many of the points made apply to Mac computers.