In regards to getting a
PR for first officers and second officers you will be on a S Pass visa that means it's nearly impossible to get the
PR. For Captains I am not sure.
Also the fleet is assigned as per requirements even if you are rated on the aircraft that SIA operates there is no guarantee that you will end up on that. Lots of locals doesnt want the 737 but many expats have ended up on the 777 as well. Usually in the interview they will be honest and they will try their best to answer your questions but again if you take the job come prepared for the unexpected. Never resign your job until the visa and contract is sorted cause immigration and the CAA is a not a breeze.
Singapore is very expensive infact the most in the world so be prepared for that.