Will it be possible to move these morphs over?... (PosetteP4-2-VickyP4?) Also wondering- can P3 morphs be moved to P4?...

P4 morphs to V2P4? No, V2P4 has a higher vertex count. You could, however, do something like this with WarriorDL's Vicky head on Posette body figure (Polly?).

P3 morphs to P4? P4 characters are cut slightly differently around the problem joints than P3, making vertex counts incompatible for some body parts. Vertex order was changed for other parts, resulting in the "exploding head" syndrome. There may be a few body parts on certain characters where this works though.

Vicki morphs will work on P4Vicki, right?

P4 Vickie is the original Victoria OBJ reworked with new JPs, so P4 morphs won't work. It's hard to say what Vickie 1 morphs will or won't work.

The head is the same (P4Vic & V2) I am pretty sure the hands/fingers feet/toes are the same A good possibility for the forearms and shins. But that's all. The morphs for the rest were lost when the geometry was recut to adapt to P4 geometry convention. P4Vic is about clothing - only clothing. You want nude = V2. It is a rare item of P4 clothing that has a fit of any sort other than standard size. If the clothing does not morph, there is no need for the figure to do it. If you have the skill to morph the clothing - you can morph the figure. (I find the figure easier to morph than clothing.) The figure simply is what it becomes, while the clothing has to closely match something else - the figure.