summer1412 - I need sleep as I write this so my brains not fully active!
OK, V4 will not take any textures or morphs from V3. I think there is to be a converter to be released for the textures so they can be used, but the morphs & clothes, no. If you purchase V4 (well it's V4.1 now) there is a V4 to V3 figure. This seems a bit daft as it means you can only use the base V3, so you can attach your V3 clothes to her but it will only be the base figure, very bland without any of the morphs. I think you can morph V4's head on this body but I can't be sure.
V4's joints are much better than V3's, still problems though, but better. I still love V3 but getting V4 is worth it because she does offer greater versatility.
Sorry to not give you any specifics but even writing this was a chore, LOL!!
I need sleeppppppppppppp................................