My knowledge of the british system is a bit rusty as I was in it over 2 decades ago, but I do not think the system has changed that much since. "O" and "A" levels are still similar now.
"O" levels refers to school upto Year 12 when "O" level examinations are sat for. "A" levels studies follow "O" level studies for two years, at the end of which one sits for "A" level examinations. Before the examinations, "A" level students make choices for Uni if they want to carry on to there. The Unis then make offers to these students conditional on them attaining a minimum of certain grades and subjects required for Uni courses (e.g. they might require a min of B in Maths, C in Physics, B in Chem,istry , etc). The students have first, second, etc choices. Once the "A" level examination results come out, Uni's then finalise their offers - first choices first, then second, etc
Uni as far as I know requires four years of study, although things like medicine may take longer.
There must be a few websites available for this sort of information like for the UK examinations council, etc.
