gimp 2.10.32 rgb / cmyk

[SKILKINKS35]

Hello ,
I have 2 questions:

1) Can I convert my RGB photos in CMYK in the new Gimp version 2.10.32 ?
    (I'm having to use for the moment an online site called rgb2cmyk.org).

2) Once a RGB photo has been converted into a CMYK photo, what happens if I want to work again on that same CMYK photo with softwares such as PAINT, PICASSA JPEGview ?
Is it still CMYK or does it become RGB again ?
(I know this may sound like a silly question...)

Thank you