You are correct for point 2, but as far as 1 goes: major depressive disorder (what most people mean when they say "clinical depression") requires only two weeks of anhedonia/decreased mood plus a few more symptoms to be diagnosed: https://www.ncbi.nlm.nih.gov/books/NBK519712/table/ch3.t5/. Which is interesting, because a significant number of mental health conditions do require 6 months of ongoing symptoms e.g. generalized anxiety disorder and schizophrenia. First line treatment is cognitive behavioral therapy and an SSRI.