I had a hysterectomy 4 months ago. All of my ovarian cyst symptoms are back. Is it okay to go back on my birth control (ortho try-cyclene low)?

Yes. Unfortunately, removal of the uterus (hysterectomy) does not treat ovarian cysts. I would recommend seeing your ob/gyn for a sono to evaluate the ovaries before restarting your pills, however. Birth control has benefits but also risks, so you would want to make sure you are treating the right thing.
Depends. You need to talk to your obgyn who did the hysterectomy - it really does depends on other potential risk-factors in taking the pill (for example, smoking over age 35, etc.) if you took them safely before surgery, it's likely fine, but you should always check with your doc first. Good luck!