Queries above all possible. You can stop contributions to an AVC and start a new AVC PRSA with a provider of your choice. You can transfer your old AVC fund into your new AVC PRSA, or you can leave it where it is. Aggregate contributions and AVC funds cannot exceed relevant limits.
Those are just the black and white answers to the queries asked. Whether or not this would be advisable would be a much bigger analysis, involving charges on both options, fund choices, personal circumstances etc.