There is a tool called an "easy-out" which requires you to drill a small pilot hole and use the easy out to back out the screw by hand. The link shows you some examples of easy-outs.
To adjust the temperature of the water in the shower, you can turn the shower knob to the left for hotter water and to the right for colder water.
To improve water pressure in your shower with a water pressure regulator, adjust the regulator to increase the pressure. This can typically be done by turning a screw or knob on the regulator. Be sure to follow the manufacturer's instructions and consult a professional if needed.
To replace a shower knob, first turn off the water supply to the shower. Remove the old knob by unscrewing it or prying it off. Take the old knob to a hardware store to find a replacement that fits. Install the new knob by following the manufacturer's instructions. Turn the water supply back on and test the new knob to ensure it works properly.
the diverter knob is either stripped or the diverter itself itself may be broken turn the water supply off take the knob off a carefully remove the diverter shaft if the flapper is missing look inside the housing for the broken piece then take the name and model down to home depot or similar home store and someone will be able to match it up,. but my money is on the stripped knob
Neither one will make any difference in water pressure.
To operate a shower with 3 knobs efficiently and effectively, start by turning the middle knob to adjust the water temperature. Then, turn the left knob to control the water flow and pressure. Finally, turn the right knob to switch between the showerhead and the bathtub faucet. Adjust each knob until you reach your desired settings for a comfortable and enjoyable shower experience.
If your shower knob is broken, you should contact a plumber to repair or replace it to ensure proper functioning of your shower.
You twist the knob.
Knob will be found in a shower.
To adjust the water temperature in the shower, you can typically turn the handle or knob to the left for hotter water and to the right for colder water. Start by turning the handle slowly to find the desired temperature.
There should be a new trim plate available and new knobs. If there are no knobs that fit the stems of the faucet, there are universal ones that go on using an adapter. A square adapter goes on the stem and is held in place with a set screw and the knob fits on that and is held on with the screw in the center that goes through the knob and adapter.
Try getting the point of a utility knife blade under the edge of the screw and pry upward as you attempt to back the screw out with a screwdriver. Once the screw is out far enough, you can grasp it with pliers and unscrew it the rest of the way. If all else fails, bore through the screw with a drill bit.