Most of the answers to your questions will depend on the specifics of your injury; torn rotator cuff injuries can range from small tears that can yield complete recovery, to large tears that cause chronic disability. Steroid injections will not heal a torn rotator cuff, but they reduce inflammation and pain, although the pain can get worse for a day or two after the injection before eventually improving.
It sounds as if your doc is trying to manage things conservatively; to reduce your symptoms and see if your body will heal itself. If the inflammation and fluid goes down you might get some improvement in mobility, but torn muscles generally take a long time to heal-- at least a few months-- so try to be patient.
I had rotator cuff surgery and it is very painful. Expect pain for at least 8 weeks. It is tuff and going to physical therapy after helps a lot. Before surgery I was given shots and they worked like a miracle. But, they wear off. I just keep getting shots until surgery was scheduled. They don't like giving to many shots. No side effects of injections for me. Hope this helps. God bless you.
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