hi there! welcome to this forum! let me answer some of your questions:
1. according to
http://www.asa.hku.hk/admission/nonjupas-uer.htm , or students holding singapore GCE A levels,
"Grade E or above in seven subjects in the first and/or second attempt in the GCE O-level examination, of which:
six subjects shall be obtained at one and the same time;
one shall be English Language at grade C or above;
one shall be Mathematics; and
one shall be a language other than English (e.g. German, French), or if Chinese/Mandarin is offered as a language other than English, grade E or above in GCE Advanced Level H1 Chinese is required; and
Grade E or above in two subjects at H2 level and one subject at H1 level (other than Chinese/Mandarin), or the equivalent in GCE A-Level examination. "
obviously achieveing that requirement grade is totally insufficient to secure a place for HKU medicine. u must, however, meet the above requirements in order to be considered by the university. i think they treat singapore GCE as the same as UK GCE (although singapore one is much tougher). since u are treated as a gap year student, u should have some A* in order to make your application competitive.
2. no your don't. faculty of medicine will help u to choose if u are offered a place. beware, HKU medicine is a 5 YEAR OR 6 YEAR program instead of 3year or 4year. if u are competitive enough, they will offer u a 5 year place. if they want to admit u into HKU but your grades are slightly not competitive as other students, they may allocate u into the 6 year program.
3. your second choice will only be considered after your first choice is rejected. that is, BDS will only receive your application information after MBBS rejects u. this is quite unfair to ppl who are rejected late as this means less time is give for 2nd choice program to read your profile. but well... this is life
hope this helps
dragon knight