GNU ARM compiler to ARM FUSA compiler

Hello,

I work for a company which develop some automotive product.

The majority of our project use the ARM GNU Toolchain 9.3.1 and we started to pass to ARM GNU 10.3.
Our project are designed to use Cmake method to call the compiler, configure the project and compile it.
To debug, we used files from PEmicro (which use gdb provided in ARM GNU toolchain)
Clion is our IDE which simply use the cmake files to compile.

But soon our systems will have to be FUSA compliant.
So we started to analyze the possibility to pass to ARM FUSA Toolchain.
But we have some question about it.

1) Is there a note or a process to make the migration from GNU ARM Toolain to ARM FUSA Toolchain ?
    Is it possible to use cmake method with ARM Fusa ? or is it the GNU layer of the ARM GNU compiler that allowed this?

2) Is ARM FUSA Free ? I see ARM Development Studio + Fusa have a price.
    But can we used the compiler without ARM Developement Studio ?

3) How I can debug with ARM FUSA ?
    I suppose the ARM Developement Studio integrate it directly, but how to do with third party (as PE micro).
    I suppose I can't simply use the PE micro files and replace ARM GNU gdb by ARM Fusa gdb.
    Is it something I have to deal with the Third party

Thanks a lot,
Mathieu