Why are pictures of different formats and why is AppIcon so important?

Question

iOS

Hello, friends!
Little by little I am mastering UITableView and faced a lot of problems:
1) Why are the pictures displayed in different formats, although I uploaded them in 3 copies.

2) Why is the AppIcon file so important? After removing it, the program does not start

3) Why is the 2 picture "Goodman Steakhouse" not displayed?

Thank you in advance for your answers, I hope you can clarify these questions for me.

Answer 1

1) Because they have a different aspect ratio and the constraints are not set correctly.
2) Because the project settings indicate that the icon will be taken from this asset
3) If you use assets, then you do not need to write the file extension. They work in a slightly different way. Use just the name of the asset
Shl. How long have I not been to Burma and Mexico City :'(