inert gas are basically having fully filled orbital.so they are highly unreactive and there is small effect.
i thinh you are asking equilibrium question.
lee chatlers principle

effect of temperature
delta H>0,increasing temperature favours reaction,because heat is required
deltaH<0 increasing temperature favours backward reaction

effect of pressure
for a reaction having more mole of gaseous substance increasing pressure favours backward reaction so as to reduce the pressure

effect of inert gases
An inert gas (or noble gas) such as helium is one that does not react with other elements or compounds. Adding an inert gas into a gas-phase equilibrium at constant volume does not result in a shift.This is because the addition of a non-reactive gas does not change the partial pressures of the other gases in the container. While it is true that the total pressure of the system increases, the total pressure does not have any effect on the equilibrium constant; rather, it is a change in partial pressures that will cause a shift in the equilibrium. If, however, the volume is allowed to increase in the process, the partial pressures of all gases would be decreased resulting in a shift towards the side with the greater number of moles of gas.

effect of adding catalyst
A catalyst has no effect on equilibrium. It speeds up both forward and backward reactions equally.

E.g.: N2 + 3 H2 → 2 NH3Here Iron (Fe) and Molybdenum (Mo) are catalysts, but the two catalysts do not affect the state of equilibrium