Okay, I have been trying out linux for the last two month.
The distro that I have tried are:
-Ubuntu
-Xubuntu
-PCLinuxOS(I think I wrote the correct name)
-Fedora Core
-Damn Small Linux
-OpenSUSE
-And a few more

And I have been trying to figure out how this unix works...(out of curiosity)

Here are my question:

Q1) Basically every distro is running the same kernel build right? (I mean from the same family "kernel.org") and the structure for the file system is the same, same booting style(except the bootloader), and everything is the same except the program that run on it(whether it is lightweight or not) then may I know what is the difference between each of the distro? Or each distro have customized kernel? If then, may I know which distro?

Q2) After tried distro, I get my hand into LFS. Have Build it for few time. I'm sure anyone who build it will be amazed by the compiling time. So, I try jhalfs (I used LFS Livecd 6.25) which included, so after finish compiling. I wonder whether the others distro only copy the required tools and kernel to the hardrive which result in faster installing time? If no, how can the installer compile the tools faster.

Q3) Is there anyway to configure the jhalfs to automatically compile all the latest tools? (assume I have all the latest tools and kernel) or is there any other tools which automatically compile and configure all the tool needed to run a clean linux? (You know, getting tired of typing command to compile each tools)

Thank you in advance for those who will answer my question.

The common thread in Gnu Linux is the use of the Linux kernel + a suite of open-source utilities that was developed under Gnu before Linux came along. Hence the "correct" name: Gnu Linux.

There can be many different versions of the kernel, and distribution packagers often customize their own. The differences in the kernels would very often not be noticed by the end user.

What mostly distiguishes distros is simply how things are organized and what desktop environment is favored. All these things can be changed (as you know from dabbling in LFS).

Distrowatch.com has a good summary of differences between distros.

1)The kernel is not usually the same version for every distro and some distros customize it slightly for their needs, In some distros they store stuff in different directories . Some distros use System V booting scripts and some use BSD style booting scripts, they don't all boot the same way