Explanation
TWBX is all in one. It contains viz, info needed to build the viz, and a copy of the data source. It doesn't contain extracts of the data but can contain both live and data extracts. Best if want to eliminate the barrier of data access.
Create a .twbx with file-based data sources
1) Select File > Save As.
2) Specify a file name for the packaged workbook in the Save As dialog box.

3)Select Tableau Packaged Workbooks on the Save as type drop-down list.
4) Click Save.
5) The default location is the Workbooks folder of the Tableau repository. However, you can save packaged workbooks to any directory you choose.
The following files are included in packaged workbooks:
--> Background images
--> Custom geocoding
--> Custom shapes
--> Local cube files
--> Microsoft Access files
--> Microsoft Excel files
--> Tableau extract files (.hyper or .tde)
--> Text files (.csv, .txt, etc.)

Explanation
It is possible in Tableau to use a sheet within a story directly.
Moreover, in Tableau, a story is a sequence of visualizations that work together to convey information. You can create stories to tell a data narrative, provide context, demonstrate how decisions relate to outcomes, or to simply make a compelling case.
At the same time, a story is also a collection of sheets, arranged in a sequence. Each individual sheet in a story is called a story point.

Explanation
Yes! It is possible to duplicate a field and add it to more than one hierarchy. Right click and choose duplicate.

Explanation
If you chose 2, then you were very close but probably didn't plot the actual Percent Difference on your view. ( One of the marks is just over the line).
* Firstly, Drop the Week ID onto the column shelf, and convert it to continuous since we need both Year and Quarter as mentioned in the question.
* 2) Next, Drop assortment to filters shelf so that we can focus on Electronics!

3) This should be your view now. Click on the Show Mark Labels icon as shown:
The final view is as follows, with 3 points below 0 ( i.e negative )

Explanation
According to Tableau's order of operations, the Extract filter is right at the top of the hierarchy. The data filtered in the Extract is then passed on to what we see in the Data Pane. See below: