Create @myjson variable as JSON type (read more):

SET @myjson = CAST('["A","B",{"id":1,"label":"C"}]' as JSON) ;

SELECT some members!

SELECT
  JSON_EXTRACT( @myjson , '$[1]' ) ,
  JSON_EXTRACT( @myjson , '$[*].label') ,
  JSON_EXTRACT( @myjson , '$[1].*' ) ,
  JSON_EXTRACT( @myjson , '$[2].*')
;
-- result values:
'\\"B\\"', '[\\"C\\"]', NULL, '[1, \\"C\\"]'
-- visually:
"B", ["C"], NULL, [1, "C"]