So the Name of the Ancient Language allows you to change the true names of other things and people

But I have a couple questions. We see Eragon can the grub worms and shadow birds there true names. So does that mean that they had no true name before Eragon gave them one? Or did he simply change there true names to something else

Also

We know that true names can describe the true nature of there associated object. But does this work in reverse? If Eragon for instance changed Solumbums name to “ bowl of liver” in the ancient language would he then turn into a bowl of liver? Does using the name of names to change a persons name actually change them?