Missing code and file name issues

[lam1aa]

• In 4.1, I had to change the CSV filename to run the code.
• In 4.2, the full code admonition don't include the final line needed to run the app.
• In 4.6, the menuitem at the top appears to be missing.
• It was difficult to download and locate the required datasets, and I initially faced problems installing/loading the required libraries in 3.4. Although they are listed in the full code admonitions, placing them at the beginning might help others avoid issues when starting the coding process.
• In 4.5, splitting the tabitem UI code into multiple parts caused errors while copying. It might be clearer to present the full tabitem code first and then explain its components.