The test about the forum rules only! The test can be multiple choice tests.
Your idea also good, i think newbie should be retricted posting before they understand the basic rules.
we don't need to go that far,
a simple redirect to
Unofficial list of (official) Bitcointalk.org rules, guidelines, FAQ after registration should be enough
perhaps an additional
"Yes I have read and understand forum rules" button to enable posting for the first time
so if they ever get banned, they cannot make an excuse not knowing/understanding the forum rules