1) If you are determined to make a career switch, 25 years old is still ok. Your career really develope and crystallise after 30.
2) Is accounting boring to study? This really depends on individual. It is not about mathematics. You need to find out yourself if you can bear with the subjects. Broadly the course includes financial accounting, cost accounting, management accounting, statistics, organizational behavior, business laws, a few other crappy laws (like succession law), financial management (like those stuff that CFA people study). I would say technically the toughest is a subject call FRE (which involves advance consolidation stuff, but this makes you understand listed company reporting very well)
3) For accounting, it is not about bachelor or masters degree. You need a qualification that makes you a qualified accountant (CPA). The cheapest route to do is in Singapore is ACCA. The beauty of it is you can work and study at the same time. You can quicken your qualification by studying full time. I think it still requires at least 2 years... i do not know these days what are the available exemptions.
4) Job search - quite easy to find a job since every company needs accountants. However, i suspect these days you have a lot more competition from migrant Indians. You see, every field has its competition, it is not a good reason to give up your existing field.
5) Career path - if you are timid you might remain an accountant forever... with little annual increments. The right way is to work towards either "financial controlling" or "business finance/analysis". The highest in the field is becoming a CFO in an MNC or partners in the big4 firms. The "business finance" field offers you
greater chance to becoming a CFO. Therefore the opportunity to go high up is there, but it depends on your individual personality. A point to note is there is huge competition from Indians.
6) Yes, ACCA is not a breeze. Assess whether you will complete the course, otherwise you be better off go screwing PRCs like Raiders.
Lastlee, the entire accounting profession in Singapore is headed by Juthika Ramanathan (you know who)