1) Planets seem to be either habitable or unhabitable. I've come across Gas Giants, but what about Volcanic, Icy, etc. worlds? Will they be in the final build?
Extreme planets will be back. There are already some techs for them in the tech tree (just disabled). However, I don't know, if only the old ones will return (aquatic, barren, heavy gravity, radioactive, toxic), or if there'll be new ones too.
2)Is there any benefit to mining a strategic resource with no colonies nearby? How far away can a mine be and still be considered effective?
Distance to your colonies has no effect on mining resources. Once you mine them, the resources will be available everywhere in your empire.
3) I haven't seen any of the nodes from II (culture, defense, etc.). I assume the strategic resources are there to replace them.
No, the old resources will be back in the form of relics. The devs have talked about them in the last dev stream.
4) Does it matter how far a shipyard is from a sponsoring colony? What's the maximum distance to receive sponsorship? Can a colony sponsor more than one?
Yes, the distance between shipyard and sponsoring colony matters. The further away from each other they are, the fewer manufacturing points arrive at the shipyard (similar to how asteroid mines GalCiv 2 worked). At least, that's how it's supposed to work. I'm not sure, if that is already the case. A colony definitely can't sponsor more than one shipyard though.
5) Will the political parties and elections from II be returning?
Yes, but not in the same way. The devs talked about them briefly in a previous dev stream.
6) At the start of a game, ship ranges in descending order are colony ships, survey ships, and finally scouts. Seems to me that it should be in the reverse order. Is that a bug or WAD?
It's WAD. The colony ship uses a cargo hull, which has much more space for life support than the tiny hull of the scout. Same for the survey ship, which uses a medium hull. Just go the details screen of each ship, and you'll see how much equipment they have on board.
And finally, is there a preferred procedure for reporting bugs?
The Support FAQ contains some useful information (especially how to report crashes). For general bugs though, posting them to the support forum should be okay.