I figured out point 1.
Nitrites can cause methemoglobinemia by oxidation of Fe2+ to Fe3+. MetHb is treated with methylene blue.
Surprisingly, this toxicity can also be used as a treatment in cyanide poisoning. MetHb loves CN more than oxygen. So, providing MetHb in CN poisoning will lead to formation of MetHb-CN complexes. At this point, Na thiosulfate is given to bind these complexes and excrete them in the kidneys.
Nitrites can cause methemoglobinemia by oxidation of Fe2+ to Fe3+. MetHb is treated with methylene blue.
Surprisingly, this toxicity can also be used as a treatment in cyanide poisoning. MetHb loves CN more than oxygen. So, providing MetHb in CN poisoning will lead to formation of MetHb-CN complexes. At this point, Na thiosulfate is given to bind these complexes and excrete them in the kidneys.