Do you actually do (system) design?

Hello,

do you (or other people in your team) actually go through a (system) design phase before you start writing code?

All of the companies I've worked for skip the design phase part altogether – can you please tell me how you do it in practice?

Do you create diagrams first, using something like C4 or UML?

Do you also create skeleton code (i.e., signatures for functions and methods) for each module / component?

How do you make sure the devs follow the designs?

Do you add the diagrams to the repo?

Do you set up the repo so that devs can't modify the skeleton code (i.e., name and parameters for methods / functions) but only add code to the body of those methods / functions?

Is there anything else you do to make the whole thing work?

Thanks!