q is short for Q:q (see below)
qq is short for Q:qq (see below)
qw qc etc. are short for Q:w Q:c and so on
:q causes general quote operators to behave like '
:qq is a bundle of adverbs :s, :a, :h, :f, :c, :b for general quote operators (behave like ")
\q in an interpolated string allows nesting of general quote operators
\q is an old, deprecated sprintf format argument