WebPlus X6: potential upgrade pitfalls

I have X2, and have built two simple sites with text, a few images, and loads of pdf files. I have recently purchased X6 as a full product, not an upgrade.

1. Can I install X6 separately, or does it force an uninstall of X2?

2. Does X6 read the wpp files of the previous sites without making any changes?

3. Are there any pitfalls or something unusual I should look out for or be aware of in this change of version?

4. If I do not like X6, could X2 read the wpp files produced by X6, or do I risk having to repeat the work if I went back? I have seen recent threads about X6 crashing, but my sites do not have large images.

Thanks