How can you arrange the elements within a group in a descending order without altering their original sequence?

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This question is not well-defined. If you're asking how to sort a list of elements within a group in descending order, you can use a sorting algorithm such as bubble sort or quicksort to rearrange the elements according to their values without changing their relative positions within the group. If you are asking how to arrange the elements in a group without altering their original sequence, then there is no way to do this, as arranging elements in a specific order by definition changes their original sequence.