Would any dr do a TURP on a cancer tumor to relieve urine flow and risk cancer spread?

Yes. This is a potentially effective solution to urinary obstruction in men with prostate cancer who are ineligible for complete prostate removal. There is no evidence that this causes the disease to spread. There is some evidence that TURP in malignant obstruction of the bladder is less effective than in cases of BPH (benign enlargement).
Yes and no. Yes a TURP opens the urinary channel so you can pee and no prostae cancer is not spread by turp.
Not best option. If younger referring to a prostate cancer that is causing obstructive symptoms on your urethra, then the answer is not likely. A TURP is like a rotorooter procedure and on a malignant tumor would only work temporarily and could actually cause more complications since the tumor will just grow back. Surgical removal or radiation or antihirmonal therapy would have more lasting results.