Tried to submit assigment. Succeesed ones but after fixed one bug didn’t get submit at all visible in notebook. There is anyway a message that assigments can be still returned before course is closed. These schedules are very confusing - is there some deadline or not in this course for returning assigments?
This seems to be some network or server problem.
Got that finally submitted and passed course 
Still need some more information about deadlines if that kind of things really exists in these courses. Some courses still waiting to be finalized.
That seems wonderful!
The deadline is just to remind you to keep working and learning. There is no such hard and fast rule. You can always reset the deadline anytime!
Yes, as Rashmi says, the deadlines are just advisory: there is no penalty for missing them. This was explained under “Course Info” on the left menu of any of the course pages.