Same question comes to my mind, esp about the last one. How do we know he/she is our friend or what he/she does if we're already died? ? Does that mean we won't know our true friends forever?
Since both of you are wondering the same thing, in my opinion, the first two should be more than enough to prove the last one, if that friend is there for you in time of need, and doesn't back bite you
for us these two should be enough that this is our true friend, and if that friend have these two qualities then the third one will be there too because for sure that friend will pray for us even after our
passing away and will not talk bad about us, some will even be there for our family when they are in need, and much more, but i think the most important is praying and do not talk ill about us,
And I would have to agree that likely if they have the first two qualities, they will prove to have the third after your death also, though we may not see that quality personally.