AML professional here with 5+ years of experience. Answering some of your questions as I enjoy helping young graduates understand about the world of Compliance/AML and get some basic knowledge under their belt.
1) Almost none required. Basic MS Office skills. From my experience, it's actually more advantageous NOT to possess the deeper Excel skillset, as anyone identified to have such skills will be pin pointed or worse, moved into a pure reporting/management information role, away from the technical aspects of AML.
2) ACAMS are geared for graduates/professionals with experience in the AML field under their belt, and looking for a physical cert that has a certain standing and recognition within the industry. ICA is mostly for individuals who do not have a degree, as it is usually recognised to be the equivalent of one in the AML world. In terms of recognition, both is deemed on par by recruiters and hiring managers.
I wouldn't advise you to shell out of your own pocket in order to get the ACAMS accreditation even before you have actual experience. Firstly, you don't even know if this is really something you will enjoy or that you wanna develop your career in. Secondly, there are many avenues to get sponsorship, the
MAS Skillsfuture Study Grant is one, and company sponsorship is another.
3) It's possible but given that you will be 25/26, you will either have to be good enough that you get promoted every 1-2 years, otherwise you have to job hop. I started out when i was 26 and im 32 this year, at my 5th bank in the Financial Crime Compliance space, drawing $8250. My next jump possibly next year will put me close to the 10k range at the age of 33. For reference, I have a private degree (no honours) and hold the CAMS accreditation.
4) No idea, never used mine before.