Uprgrade to Framemaker 11

1. Yes, as asked.
   
   FM6 files open fine in later FMs, as long as you aren't using certain custom extensions (macros, scripts). If porting forward is all you need, I can't think of any considerations. However, as Jeff points out, the internal binary format will be rewritten and once resaved, cannot be re-opened in FM6. You can save as MIF, which can be at least opened in FM6, but  FM8 and later will convert some characters to Unicode (UTF8), and will not convert them back when saving to an old MIF version.
2. According to Adobe's product page, the Upgrade product is available in French or English.
3. For FM11, it appears that the discount is limited to users of FM9 or FM10. I'm still on FM7 at home, and as I recall, the upgrade discount slipped out of my reach at FM10.

1. NO – FM6 files will be upgraded & the only way to get them back into FM6 is via MIF

2. Probably

3. Nobody here’s going to know that – it’s a user-to-user forum; contact your local reseller or Adobe directly