My experience with Creo toolkits is that they are consistently forward-compatible. That is, if you build it on Creo Parametric 2.0, it will also run on Creo Parametric 3.0 and later. I have two applications which use both Creo Parametric Toolkit and OTK C++, and the versions I built on Creo 2.0 ran without issue on Creo 3.0.
However, you should not expect to do the opposite: If you build a toolkit application on Creo Parametric 3.0, it will not run on 2.0.
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