Student responsibility for synchronous online assessments Here are constraints for my course (which will be delivered remotely):

The class size is huge (250+ students).
Lecture contents will be delivered asynchronously (with pre-recorded videos and live Q&amp;A sessions).
Synchronous (scheduled weekly for 20 minutes), frequent, small assessments will be used to test lecture contents.
Each assessment is web-based and can be automatically graded (say manual grading is not possible, given the TA hours, for this large class).

Given that it's an online course, is it fair to assume the responsibility of stable internet connection (so that each assessment can be started and submitted in time) on students?
If such an assumption is not fair, then does it mean any student claiming a network-related problem can be accommodated unconditionally for extra time or another test?
This is something you need to work out locally and before the course starts if possible. People here will have opinions, but only the local opinions at the university will have any actual weight.
Some things here seem foolish to me. Especially a large student population with insufficient TA support. There should be a dozen or so TAs to make this possible. Harvard's CS 50 course is also huge, but the student to staff ratio is about 20 to 1.
It may not be fair for the course designers to make such assumptions but you are probably going to be stuck with them whatever they are.
You point out some of the deficiencies of online instruction at this time. Even worse is that some students just don't have access to the equipment or bandwidth. But it is a chaotic situation.
Probably the best you can do is file a statement, say with a department head, and get acknowledgement of it that (a) internet connections can be flaky (b) cheating can be rampant no matter the technology (c) policies need to be established to fairly account for as many of the potential problems that might occur. And the policies will need to be somewhat flexible.
But demands are likely to be ignored. Enter into a conversation so that you have some assurance that fairness will be maintained.
On the other hand, some things about this course seem fine to me, such as frequent small assessments rather than a few high risk exams. Question-answer sessions is also a good idea if the times are flexible. Mailing lists can also be used to increase communication.
The course may actually need to oscillate a bit toward a successful outcome as there has bee insufficient time to even design the research needed for successful pedagogy. But if those assessments are well designed it can work out.
And you should prepare a quiet place in which to work if that is at all possible. Especially for the assessments.