Those are just the basic 'seek advice' guidelines... I think it's safe to say that, once it gets to stage 2, the symptoms are quite distinctive...
Ex wife tells me: Splitting headache that won’t quit. Total loss of sense of smell and taste. Chesty cough that brings nothing up. One pupil that does not react to bright light, doesn’t dilate, just stays the same.
She is on the mend now, and the headache has gone after a doctor told her to take ibuprofen, not paracetamol.
I have read that ibuprofen feeds the Covid, so that’s probably another Facebook myth disproved.