Do the symptoms (rash, etc.) of inflammatory breast cancer come and go? I've had breast cancer in my right breast and got a rash in my left breast two

It's hard to comment without seeing it, but in general terms a rash that is related to the progression of cancer does not come and go, especially over many months and several years. It is unlikely to be related to cancer. There are many other things that can cause a rash on the chest wall, so one would have to place this in context of all other symptoms and circumstances of that rash.
It sounds like you have had a previous diagnosis of breast cancer, so you may be connected with a breast surgeon who would probably be in the best situation to evaluate that rash.