1. MSC = Mass Storage Capacity, in which your player is seen by your computer as an external drive; MTP = Media Transfer Protocol. MSC is especially good (and necessary) for systems not up to spec with the Clip’s requirements, such as older (but still not that old!) PCs, Macs and Linux-based systems. A somewhat universal system. However, MSC cannot be used with DRM’ed music–music protected by “digital rights management,” such as Rhapsody music or music bought at many Internet sites, which tries to protect uncontrolled copying of the music (and the possible loss of resulting sales). Neither is better or worse, but one may suit you more than the other. I use MSC mode, so that I more easily may use my player on different machines of whatever types. Of course, as you know, you readily can change the mode used to connect to a computer, at any time (but see the note below). There are some other advantages to MSC mode, such as when your computer needs to see a drive to run software on it (such as to normalize your music, with MP3Gain).
A “trick” with the modes: files transferred to your player under one mode are not seen by your computer when you are hooked up under the other mode (although everything is seen by the Clip)–hence my preference to stay under a single mode most of the time.
Autodetect will hook up in the mode that is possible. I believe it defaults to MTP and then “falls back to” MSC if MTP is not possible.
2. To re-set all your settings, such as when you made changes but can’t remember what you did and want to get back to the original settings and a clean slate. Good when you made a lot of changes and things are not working out, although I don’t think that the Clip is all that complex that this feature would be needed much (if at all). Re-set does not erase your files. (Format under settings will erase your files.)
4. To stop play (a Sansa idiosyncrasy): use the play/pause button (the top of the wheel) and press to put the file into pause. You also simply can turn the player off, if you’re done using it.
5. It will shut the player off (I believe)–that’s the purpose.
7. The battery will last 300-500 full charges (not partial charges–partial charges will make up a full charge). You can check out batteryuniversity.com for helpful information as to batteries, some of which was summarized here by a member. It would be nice if the battery easily could be replaced, but that would add bulk (my last Sansa used a AAA battery–very handy and nice, but larger). In the end, even if you fully charge every day, the player would last 1 to 1-1/2 years; you more likely would be charging every few days, getting at least 2-3 years of use. And by then, quite candidly, more robust players will be out. Many have posted tips here as to how to lengthen the life of the player, both the battery and the screen (which has a life of about at least 5000+ hours).
I hope this helps. You made a good choice–enjoy!