I think yes. Some says ago someone uploaded a V4 freebie with a pz3 scene. V4 appeared inside with a nice texture and lights... and the three male morphs completely working (I have V4.1)

I suppose if anyone exports a scene with V4.2 and A4 morphs injected in her, a V4.1 owner could open it and A4 would work too

Theorically.-

CASETTE
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"Poser isn't a SOFTWARE... it's a RELIGION!"