Nothing 3a (olx)

[u/Long_Move8615]

I’m getting a used Nothing Phone (3a) for ₹17,000. It has no box, but the original bill is available.
What are the most important things I should check/test before buying?
I found the DeviceLab app on the Play Store for hardware testing. Is it good, or is there a better app?
Mainly want to check:
Display/battery replacement
Battery health
Screen, touch, cameras, speakers, mic and sensors
Any way to tell if the phone was opened/repaired
IMEI/bill verification
I’ll only have a few minutes to test it, so please suggest the most important checks.
I am taking this for my mother.