I am assuming that all projects are solo, correct?
Yes. Students are certainly encouraged to discuss problems and general approaches to a solution, but everyone needs to write their own code and writeup. Please read through the Collaboration Policy on the course info page.
Can we know about the midterm date?
As Jim stated in class, the (currently unofficial) date for the midterm is set to October 17th.
What is an example of "other contributions to class"?
Check out what we say on the course info page: "The remaining 2% of the participation grade will be based on in-class comments, Piazza discussions, participation in office hours, and other contributions to the class (at the discretion of the instructors)."
"Other contributions" could also include serving as a Human Processing Unit (HPU) to generate a 2D representation of a cube. :-)
Are private comments counted into class participation?
Private comments should be reserved for questions about grades and other private matters. One of the aims for having everyone participate in online discussions is that others can benefit from your comments and questions! So let's keep it public. :-)
Course Info: "To earn the first 3% of your participation grade, you are required to make one question/comment on each set of lecture slides, via the 462 webpage. In order to receive credit, this comment must be made prior to the beginning of the next lecture." Sadly I have already forgotten that once. Is the grade function continuous (or is there a tolerance)?
Missing a comment here or there is pretty minor (about 0.125% of the total grade). There are enough bonus credits in the assignments to make up for it.