Can you make a best friend after 40?

Nope theres a sign outside the door of life that says

"nO FrIeNdS aFtEr 40"

Of course; very common in fact.

I even found true love after age 40 as well...

Yes, even old people become besties in retirement homes.

Yep. The term may be associated with children, but everyone with at least one friend has a best friend.

No, after 40 it's only worst friends