Yes, to all your questions.
Here is the relevant discussion from CGEL (p. 1743; note that asyndetic means that the coordination in question does not use an explicit coordinator such as and, but, etc.):
Asyndetic combinations of main clauses
…
■ Colon
[18] i Roosevelt was not a socialist: his
solution was not to eliminate capital, but to
tame and regulate
it so that it could coexist harmoniously with labour.
ii He told
us his preference: Jan would take Spanish; Betty would take
French.
iii The rules
were clear: they were not allowed to speak to the committee
directly.
iv Brown pointed
out the costs to the community on the radio last night, and
McReady mentioned
the political consequence in this morning's paper: the bill
will cost
the taxpayers more
than $100,000 in the first year, and may be seen
as giving the
Republicans an unfair electoral
advantage.
The colon, we have seen, is not used in syndetic coordination, and in
aysndetic combinations it indicates an elaborative rather than
coordinative interpretation. What it elaborates on may be a whole
clause, as in [i], or a smaller element, such as his preference in
[ii] or the non-final NP the rules in [iii]; indeed, there may be
more than one such item, as in [iv], where the clause following the
colon elaborates on both the costs and the political consequence.
Like the comma and semicolon, the colon can separate a
positive-negative sequence, where the first clause contains not +
only/simply/merely/just:
[19] The Romans built not only the Fort of Othona: they had a pharos,
or lighthouse,
on Mersea.
This does not invalidate our statement that the colon cannot be used
to separate clauses in a coordinative relation. It is, rather, that
the elaboration relation makes perfect sense in this context: the
second clause provides an explanation or demonstration of what is said
in the first clause. Note, then, that it would be quite impossible to
insert but after the colon.
