I have been on google and seen people pass a home urine test after 2 weeks despite smoking for months and years everyday. I assume then that they are not very reliable.
Why would you assume that? Home test kits function on the same principle as the assays the labs use for the initial screening. Obviously, the labs still find them reliable enough to merit continued use.

But i found this one : This test can detect and identify traces of up to 10 gms drugs in the persons urine.
Youre thinking of the GC/MS. No big deal here. By utilizing the Forum Search button, using the terms "functionally equivalent metabolites", you'll discover why the GC/MS tests at a numerically lower cutoff threshold than the I/A screen, and that the two types of tests are functionally equivalent.