Hi @ga.imparato,
1, With the first question:
I am not sure that you can use it like that. Maybe you will meet issue or error when using compatible versions, it’s better that you should use legato and yocto with the version as Sierra suggests.
2, With the second question:
The link for downloading the Linux Distro Source is not working now.
Probably you need to try later.
Please refer to Link is dead - #2 by Donald
Please help to tick “Solutions” if your question is answered.
Thanks,