The brutal truth is that most of us are quite weak when it comes to asking questions. Given the age-group with which you're working, I'm a little surprised. I thought youngsters a little less ego-defensive.
In my experience with MOOCs, grads seemed to ask questions constructively: I was doing 'this', expecting 'that' (most often, what the coursework predicts), but 'something else' occurred. When the demography changed to more 'ordinary people', the quality of questioning declined.
Hey, even my first-before-all-else position as telephone 'TechSupport' to my mother, suffers from this problem: "how did it go?" "Oh, I did that but nothing happened; so I'm just waiting" or "press the Menu button", "but I can't see a menu button on the keyboard" - and she's ninety, not nine! (and had better not ever read this!)
I'd consider it rude were one of my tutors to say things like: "you have to tell me 'everything' because my crystal ball is broken" despite the (massive) temptation to do so. Take a deep breath before responding - even help someone else before coming-back to 'the problem'.
Also, if you are receiving 'the same question', that may indicate a 'gap' in the materials. Similarly, there is no harm in answering 'Barney's' "similar question' by referring him to the response you gave 'Fred'. In fact, it may encourage them to help each by answering each other's questions (collaboration, social learning, ...) - but I presume you have some sort of 'bulletin board' discussion environment cf one-to-one email or similar.
Your students (and many of my vocational trainees) are used to having you/someone 'right there'. So, remote work is a big change for them too. Frustration will arise! Meantime, don't discount your own frustration at trying to help but being unable to see even the slightest hint of what (s)he's doing and the results thereof!
I have found that giving out pages of HowTo advice at the beginning of a course is largely wasted. Probably because there is so much (other) 'bureaucracy' at a time when most are feeling 'enough already! Just get on with it...'. Even(?) university students are guilty of this. When we refer them to such hand-outs, the excuses come back thick-and-fast - inevitably, "I didn't read it".
Accordingly, you might like to devote some time to explaining 'the new normal' during your next class - perhaps a 'filler'/break in-between major teaching-objectives; or whilst giving pause before repetition.
You could even give them an assignment to do with a member of their family - the student is blind-folded or facing the other way/into a corner, the other operates the computer or carries-out some common (multi-step) task but with "dumb insolence" (only acting literally, to the letter-of-the-law). It's a 'what is computer programming' exercise, but questions are a form of instruction too! Thereafter link the lesson-learned to question-asking skills on-line...
Also, remember how last-minute-merchants tend to be in a state of 'panic'? They may not intend to be quite so rude or to give opaque descriptions. Sometimes addressing the person 'behind' the question can help. Once the trainee has settled, a more meaningful conversation should follow.
Which brings me to the suggestion that (I'm assuming assignments span days), it is a good idea to ask a question which encourages thought about the assignment on (perhaps) a daily basis. Firstly, you are encouraging an early start (we can but hope!). Secondly, repetition is a key to 'learning' (apologies!). Thirdly, you help kids who don't have self-organisation skills, which they will also need to be learning if this is their first on-line course! However, the big-win is that with 'good design' of your reminder/follow-ups, it should start to encourage questions to take the form: 'you know how you said... well when I tried... and this is what happened... How come?' which helps to create exactly the structure for which you yearn!
(well OK, sorry but nothing's perfect!)
You may like to take a look at https://blog.edx.org/tips-for-successful-online-learning/ plus its links. There used to be a free, not-for-credit course as a gentle introduction to learning on-line, but my quick-look, just now, failed to spot it. NB that course took a trainee's point-of-view cf the plethora of 'transitioning to teaching on-line' courses aimed at teachers! (that said, if you've never been trained to present on-line, might such a course include exactly this question?)
Try also https://www.futurelearn.com/using-futurelearn/why-it-works although that seems to be the hows-and-whys of their implementation of many of Hattie's ideas and philosophies. They also offer https://www.futurelearn.com/learning-guide as a PDF or epub (registration required) but you would have to heavily re-word this before use directly with students in such young age-groups (use with their parents might be another and valid approach though)
Welcome to this brave, new, world! All the best... =dn
(Disclaimer: I have used the edX platform to present (and answer questions) for many years)