Dcoded
If you move between any AOC you will need to do an AOC 2 AOC conversion, this is straight forward as the AOC are now very similar and it is an objective to be able to fly on the various AOC seemlessly in the future.
You will do your training wherever the training capacity exists, so yes you could be released to line then back in the sim to do an AOC change followed by a further line check, not ideal for either party I know, but them is the rules.