will cs4 work on high sierra

Adobe CS4 apps are now very old so don't expect them to be compatible.

Have a look at the screenshot below, it is from https://roaringapps.com/apps?platform=osx

Drag the screenshot from this post and onto the preview icon on your dock to get a better view.

You could partition your iMacs HD and install High Sierra to the new partition and boot between the two when you want to run your CS4 apps. Also you could install High Sierra to an external drive, or move your existing OS and apps etc to it depending on which OS you want to be your primary OS.

I upgraded, while I was in the middle of a job being done in illustrator CS4... what the heck was I thinking. CS4 apps did not work in High Sierra (I was using Sierra with few problems). I decided to go back in timemachine and to the day before when everything was ok and it crashed in the middle of the task. I tried to do it again, My HD was no longer visible. I had to take it to a mac genius bar and have them get it working again, thank goodness for extended warranty and my timemachine back up. They erased HD and put the Sierra back on and I used my timemachine back up to reinstall all my missing files. CS4 was working again.

Mac OS 10.13.1 has made my InDesign CS4 inoperable. Tools are no longer visible. Program doesn't function.