Hi Hüseyin! 1-2) In my experience If you are a Mobile Applications Developer you will have the following responsabilities: - Develop (not designing) both functionality and screens of the app you are working - Consume (not develop) third party or self company owned APIs or Backend services - Distribution tasks. - Mantainance tasks. Now, there will always be companies wishing you know the whole thing (ui/ux, backend, frontend, mobile, cd/ci, data science, etc.). And of course it will be helpful for you to know a little bit of the stuff around mobile development, but it's not very common since it's not part of the responsabilities of a mobile app dev.
3) No, you are not responsable for the designs of your application, that's why companies have Product designers, ux designers, ui designers for preparing the screens, logos, color palettes, etc for products. As a developer your job is to see and examine the designs and take them from Figma, InVision, Zeplin, etc to the Code editor.
4) This is the thing, if you are working as a Mobile Developer you might know about Mobile development, not backend, not frontend, not ui ux. BUT if you know a little about backend that might be helpful although backend should not be your responsability.
I hope this makes sense to you. Cheers!



