Dr S Bhatia

Just as Art said this is very much possible. Both, course as well as each individual quiz can be password protected, network address can be specified and some activity locking is also in mode. Security wise, moodle has very little to complain about, if at all

That's perfectly fine. We understood that. What you need to understand is that grade coding depends upon HOW would you want to grade it? see e.g.

Q. If we divide 15 by 2, then:

1. quotient is 8
2. quotient is 7
3. quotient is 6
4. remainder is 1
5. remainder is -1
6. remainder is 2

Now correct replies are 2 and 4. are you ready to give 50% marks if the student replies (2 and 5) or, (3 and 4)? if yes, it's possible in moodle.

If you want to give zero if only one answer is correct and require that all answers be marked to get the grade then that is as yet not available in MCQs

Workaround: instead, have a cloze type question/short answer question which says:
q. If we divide 15 by 2, theninstruction: write the answer in the text box in the following format :write quotient first, followed by remainder like [2 5].
this way, unless they give all answers in the correct desired form, they get no marks.

Glad to be of any help

Joseph is right that xml is the best format but from personal experience and popularity, the xml is somewhat low because it's prone to errors such as yours. you did not have to do anything with it yet the export file was corrupted. So try what JR has suggested and let's hope it works for you.

Unless space is a constraint, three courses is THE option.
The principle behind this is called :
KISS- Keep It Simple, Stupid.

p.s.
(stupid should not be taken literally please; Just kidding)