For sure you cannot use yellow hose for high pressure. If can, then karcher pressure washer will not come with that black hose

Even in this picture I did not think that the hose can stand even 100bar. Maybe you can ask hardware shop for hose that can withstand the pressure you want.

Yes high pressure hose is rigid because it has braided fiber inside.

Maybe I was wrong since when I Googled I can see picture of blue hose that looks similar to the one in your picture that can stand 3000 psi which is around 200 bar already. I think it is still quite rigid but yes no matter how flexible it is once you turn on the machine it will become more rigid.

My original black hose after few years also become stiffer and then the pvc insulator (outer shell) cracked and crumbled. I bought replacement on Shopee online which is longer.