Read https://wiki.ubuntu.com/DerivativeDistroHowto
I changed everything in Ubuntu like name, screenfetch logo, etc., but I failed when it comes to creating an iso for my OS.
Modify the Pretty Name Variable in /usr/lib/os-release and change "Ubuntu" to the name you prefer. For changing the icon, run:
sudo cp -r /usr/share/icons/hicolor/256x256/apps/ubuntu-logo-icon.png /usr/share/icons/hicolor/256x256/apps/ubuntu-logo-icon.png.bak
And then place the logo's .png file in /usr/share/icons/hicolor/256x256/apps/ and rename the .png file to ubuntu-logo-icon.png.
I want to change everything like bootloader logo .
I assume you are talking about the boot splash screen, right? See How do I change the plymouth bootscreen?
You can get one Plymouth them from Pling or create your own theme.
, bootloader name, etc. I don't want to show any Ubuntu name in that
See How to safely change OS name in grub boot menu? You have to modify /etc/default/grub.
Which tools/packages do I need to install for that?
A.F.A.I.K, there is no such tool/package.
I also want to change the grub screen.
I presume you're talking about the Grub theme. You can select one theme from
Pling or create your own theme.
In particular I want to know which tools are generally used by Lubuntu/Xubuntu teams when they make their OS from an Ubuntu build.
They don't really use any tool, they modify the files and repositories themself.
