Rpm Goes Up To 3k When Press The Clutch

Assalamu Alaikum
When I started my Corolla Xli 2011 model in the morning, the RPM was higher than normal and I knew the reason as the RPM was higher due to the cold engine in the morning. When I run the car, I pressed the clutch during driving in order to change gear RPM went up to 3K. when I changed the gear, and released the clutch, the RPM goes normal. I got the car neutral, when RPM goes up and I removed the foot from the clutch pedal, acceleration pedal and brake pedal, the vehicle run on the road neutrally and RPM is still on 3K. I pressed the brake pedal and the car was stopped and RPM came back on 850 and I faced this issue, when I drive the car.
I went to the mechanic to get checked my car to settle this issue. He told me that throttle body needed cleanliness. The mechanic cleaned the throttle body, spark plugs, air filters, and he also calibrated the car with IT device. When he did the test drive, the same issue appeared once again.
I contacted with another mechanic and told him the issues with my car. He also said that the throttle body was not working properly and you need to change the sensor. He changed the whole throttle body with sensor, air filter and spark plugs and he cleaned the air flow sensor. When he also did the test driver, the issues were remained there. I do not understand the problems of the car so please help me in understanding the issues of my car. When RPM reaches on 3K, the engine of my car creates more noise and the situation is becoming very alarming.