Welcome. It takes a bit of time to learn it all but I will try to assist.
1. To change instruments in TTS:
http://www.herbhartley.com/hh2_edited_slimmer_005.htm my web site page tells how to do that...ignore that it's talking about MC4&5... 6 with TTS is very similar. As a side issue...I would use CakeWalk Sound Center since the instruments sound better.
2. Delete a track and 2 go away.... don't panic, use EDIT UNDO to get them back. MC will delete whatever tracks and or clips you have selected, so you likely have several tracks currently selected. Select only one and then delete.
3. I don't use quantize. You can drag the notes but be sure the resolution is set to the shortest beat duration you plan to use. That helps to land notes where they need to be. If you right click the note in STAFF, it pops up a note properties window that lets you be very precise in what editing you do.
4. I don't use piano roll..... so, maybe to let you know what you have edited.... or just to look pretty?
5. No clue
6. Probably.
7. Click and drag them in the track view or the console view. I think you have to grab them in the left side inspector area..... but yeah...easy to do. Same deal in console view.... grab and drag.
8. IDK
9. IDK
10. See my web page again.
11. again IDK..... I rarely (as in never) use PRV to edit midi. I prefer STAFF since I am more comfortable reading the staff.
we have a few PRV experts here that can answer those questions. While I have used MC for many years, I tend to use and know the parts of it that I work with on a regular basis.
That is certainly a lot of questions, and I hope I have shed some light on the answers. Feel free to ask more.