Why does the rate of any reaction generally decrease during the reaction?

Kindly go through the solution 

$K=A.e^{-Ea/RT}=\left(6.5\times 10^2\right)e^{-26000K/T}$

$\frac{Ea}{8.314}=26000$

Ea = 216.164kJ/mol $\cong$ $$ 216

Reaction rate is used to measure how fast or slow reactions occur per unit time. The rate constant is a proportionality factor that remains constant for every reaction.

Yes, in elementary reactions, order and molecularity can be the same, but this is not always the case because order is an experimental quantity, and molecularity is a theoretical concept.

Reaction Kinetics, also known as chemical kinetics, is the study of the rate of chemical reaction and the factors affecting the reaction rate, such as temperature, concentration, and catalyst.