The question is... about LFS (Linux From Scratch), if I would build a Linux system, with LFS, is it 100% mine? Could I say I made all this from scratch?
No, of course not. You did not write any of the software, you just compiled it. All the licenses and copyrights that the software was distributed with apply to an LFS system just like any other.
You can only claim to have done something from scratch if you really wrote the software yourself. If you just bundling some software you can give the bundle/distribution a name but that's it.
If you expect to receive karma points/get famous/improve your cv by creating a distribution and just giving it your own name you are mistaken. It can even backfire if people look at your distribution and create a shitstorm because you are just rebundeling LFS/other Distribution.
If you are serious about creating your own distribution you should think who your target audience is, what you want to do different than other distributions and how you difference yourself from others. Afterwards you can try to create a derivative from existing distributions (or creating a complete new one) based on your objectives.
Please bear in mind that creating a distribution is different than creating your own system as you should provide security support, provide different architectures, have knowledge about the kernel (which modules make sense for a wide variety of hw systems), early boot stage (debugging initramfs), bootloaders (efi, iso boot, hdd), different build systems (make, scons, cmake, jam, ...), hardware architectures etc.