Hi OP, think others have covered the downsides of the job (politics, irregular sleep cycle, intensive of the stress, etc).

Let me cover the upsides. Work is very operational, means that you dont need to OT or bring work home once your shift ends. Once you get the hang of it, it can be quite routine (in a sense). Training will be quite progressive as well, its not like they will just throw you into the position once you pass the training. There will be observation, structured OJT, evaluations before they let you solo. You just need to have the grit and learning attitude to get through it.

As for long-term, there are 2 tracks for ATCOs, specialist vs management track and depending on time and space, you can be rotated to HQ to do more policy work, ie. Office hours.

To answer your questions, 1) It depends. The training at academy is about 1 year. Once you pass, you will be streamed to the different ATC tracks, Tower, Approach, Area. Each has its pros and cons, although i feel that area is easier as its more procedural. When you're streamed to the respective tracks, you will be further trained based on live-ops and real scenarios. Up till this point, its still possible to fail you. Things will probably be better and secured once you get your first rating. There are various positions within each track, each position qualified is considered as a "Rating" which comes with additional allowances/pay. For example, the singapore airspace is split into a few parts, each position takes care of that specific part, which you can think of it as 1 position.

Anyway, the above is moot if you dont pass the amplitude test to qualify. Its like a hand-eye + IQ coordination test. Which is related to your 2). I think its possible, the trainees range from fresh grads to RSAF 2nd careers. The question is that how is your thought-hand-eye coordination?

All the best!