Why can't tasks be added or canceled in the current iteration?
The current iteration is agreed with you on the volume of work, deadlines and budgets. To cancel the task, we need to do some work. To add a task, we also need to do some work.
My project does not fit the description of your examples. I do not understand the description of your examples.
You can describe your task in the "Extra Information" column of the order form. Perhaps we are competent in its solution.