iATKOS | United Kingdom

I have an early 2015 macbook Pro, with a 13 inch retina display, and i have 2 questions.

1.) Can I partition an external storage device, and create the bootable installer on the partition without formatting whole the drive?

2.) Am I able to partition the internal storage, and create the partitioned space the installer for Sequoia?

(These questions are unrelated, one is because i don't have a big enough flash drive, and the other one is because i have a 2tb drive with like 1.8 tb free, but it has photos that aren't backed up, and i am unable to back them up.)