Fix minor typos and output errors in Day 13

[HariKrishnan-Ramesh]

Hi Asabeneh!

First of all, thank you so much for putting together this amazing "30 Days of Python" challenge. It's an incredibly helpful resource!

While working through Day 13 (List Comprehensions), I noticed a few minor typos in the code comments and outputs. I've created this PR to help polish the document.

Here is what this PR changes:

• Fixed a duplicated heading (Example: 2).
• Corrected the commented outputs in the tuple and filtering examples so they perfectly match the code logic.
• Added a small example to understand the condition if....else with list comprehension.
• Fixed a small typo in the output for Exercise 6 ('Yetaeyeh' -> 'Yetayeh').
• Added a tiny hint to Exercise 4 to help beginners understand they need to slice the string to get the country code.

Let me know if you need me to change anything. Thanks again for this awesome repository! 🚀