Fellow forum members,
Thank you to all for your postings. I am still trying to figure out how to correctly install Bitcoin Core 0.18.1 onto a new Ubuntu 18 LTS installation. In an effort to understand, I have watched the "How to install Bitcoin Core wallet in any Linux distribution" YouTube video in the link below:

https://www.youtube.com/watch?v=Sw-L5hsoUes&app=desktop

The instructor in the video does the following steps:

1. Extracts the tarball file onto the desktop.
2. From the BIN folder he drags the Bitcoin.qt file over to the desktop.
3. He creates a new Bitcoin folder on desktop.
4. He moves the Bitcoin.qt file inside to the Bitcoin folder.
5. He moves the Bitcoin folder to the Home folder.
6. He opens the Terminal and uses the "cd" command to move to where the Bitcoin.qt file is at.
7. He uses the "ls" command to confirm the "bitcoin.qt" file is there.
8. He makes it executable by using this command: "chmod +x bitcoin.qt"
9. Then he launches the wallet by using this command: "./bitcoin.qt"

Can anyone in this community please help me with the following:

a). I followed these steps to the letter on my new Ubuntu 18 LTS system and it does not work.
    Is this installation method the YouTube video covers compatible on Ubuntu 18? Is it suppose to work?
b). Why does the YouTube instructor use the command below:
and not the command below mentioned in: https://bitcoin.org/en/full-node#linux-instructions and shown below:

c). I do not understand why the YouTube instructor does not move the other files in the BIN folder to the newly created Bitcoin folder mentioned in Step 3? Why does only the "bitcoin.qt" get moved to the HOME folder inside a folder named "bitcoin" and the other files in the BIN folder get left behind?  I find this confusing and I hope somebody can clarify it.

d). Can anyone please post the correct steps everyone needs to follow if the goal is to correctly install Bitcoin Core 0.18.1 onto a new Ubuntu 18 LTS installation. I just need it explained as steps because that will help me a lot. Therefore, I hope somebody can post numbered steps so everyone needing to perform this task can benefit. 

e). Lastly, from what I have learned so far there are three ways to install Bitcoin Core:
For example:
#1 You can download a source tarball and install it manually.
#2 You can download a .deb file and install it manually, using dpkg or the Software Centre.
#3 You can find a PPA or a third-party repository, and install it from there.
Which of the three methods listed above is the YouTube instructor using? 


Thank you very much in advance for any postings.