Is temperature basically a constant heat supply? There is a little thing that I am sure about temperature (and how it affect energy level) so I made assumptions. But do not know if they are correct or not
From what I know
- Temperature = constant heat supplied (constant energy supplied).
- Temperature does not exist when temperature is 0 kelvin (absolute zero), which means no temperature
=> This explain why atoms still move at room temperature because there is always energy supplied from "temperature" or heat supplied. The more heat is supplied, the faster the atoms move. The only case that has no "temperature"/ "energy supply"/ "heat supply" is 0 kelvin (absolute zero) .
=> If we heat an atom to some point, it's excited. But afterwards, it is in its ground state again.
So from what I know, there are 3 things unclear to me.
1) Temperature = Constant source of energy supply = constant source of heat supply. This is the reason why we say that in the natural environment, atom will not stop moving ( As there is a constant source of energy supply).
2) "If we heat an atom to some point, it's excited. But afterwards, it is in its ground state again". --> In this case, we can fix the problem, we can make the atom always excited by constantly heating it or another way (this way I am not sure) is put in an environment with the suitable temperature that can make it "always" excited.
==> According to what I see, the method of heating is temporary but the method of putting it in an assuming environment with suitable temperature is a forever method (theoretically)
3) If the temperature is 0 Celsius there still exists temperature. But if the temperature is 0 K, theoretically, there will be no energy or heat supplied, making the atom stop moving (although electron still move as cloud of electrons). Am I correct ?

Many thanks.
 A: There is a basic confusion between classical thermodynamics, in which framework temperature is defined, statistical mechanics from which the thermodynamic equations emerge, and quantum mechanical systems . Classical systems emerge from the underlying quantum mechanical but terms should not be confused. Temperature is a  classical thermodynamic measure.

Temperature = Constant source of energy supply = constant source of heat supply.

this is the classical thermodynamic temperature, a measurement:

A temperature is an objective comparative measurement of hot or cold. It is measured by a thermometer. Several scales and units exist for measuring temperature, the most common being Celsius (denoted °C; formerly called centigrade), Fahrenheit (denoted °F), and, especially in science, Kelvin (denoted K).

you continue:

This is the reason why we say that in the natural environment, atom will not stop moving ( As there is a constant source of energy supply).

No, here you are confusing the underlying statistical mechanics underlying level, which has different quantities measured, namely kinetic energy, and it is the average kinetic energy that is connected with the classically measured temperature. There is an average kinetic energy distribution in a system, but unless heat is inputted in a system with temperature T it will slowly cool. This is an animation of an ideal gas system in a box, there is a distribution of velocities, and the average of this enters the temperature equivalence to thermodynamics formula .

You continue:

"If we heat an atom to some point, it's excited.

Heat is a classical thermodynamic variable. An atom is a quantum mechanical form and cannot be heated. It is excited by interactions with other atoms and returns to the ground state radiating a photon which will cool the ensemble eventually as part of the black body radiation. In your diagram the atom goes to level2 by having interacted with another atom absorbing some of the that atoms's kinetic energy appropriate to the energy difference between 2 and 1.

But afterwards, it is in its ground state again". --> In this case, we can fix the problem, we can make the atom always excited by constantly heating it or another way (this way I am not sure) is put in an environment with the suitable temperature that can make it "always" excited.

Again the confusion of frameworks.
One can heat an ensemble (thermodynamics) and thus keep the temperature constant and thus keep the atomic distribution of velocities constant.

If the temperature is 0 Celsius 

0 C is 273K. It is just different scales.
there still exists temperature.

But if the temperature is 0 K, theoretically,

Quantum mechanical rules exclude the exact 0K, 

there will be no energy or heat supplied,

Quantum mechanically there will always be some kinetic energy 

making the atom stop moving

as the other answer  says there is the Heisenberg uncertainty, if an atom is completely at zero momentum, it will be undefined in space, so it cannot completely be at zero kinetic energy.

(although electron still move as cloud of electrons). 

The electrons are in  quantum mechanical orbitals and those are probability loci and they will have energy but the term "motion" is not applicable.
A: 
1) Temperature = Constant source of energy supply = constant source of heat supply. This is the reason why we say that in the natural environment, atom will not stop moving ( As there is a constant source of energy supply).

No. The atom will not stop moving at T = 0 because of Heisenberg's Uncertainty  Principle,  (in that we cannot know the position and momentum of a particle simultaneously). Temperature is not related to a constant source of energy, as we can keep a system very well insulated and it will retain a given temperature with needing energy. Eventually, as there is no such thing as a perfect insulator the energy inside the system will change, depending on the outside conditions, but I don't think this is what you mean in your question).

2) "If we heat an atom to some point, it's excited. But afterwards, it is in its ground state again". --> In this case, we can fix the problem, we can make the atom always excited by constantly heating it or another way (this way I am not sure) is put in an environment with the suitable temperature that can make it "always" excited.==> According to what I see, the method of heating is temporary but the method of putting it in an assuming environment with suitable temperature is a forever method (theoretically)

I am not sure what you mean by this. In thermodynamics, heat has a specific definition, but what you seem to mean here is radiation in general, which will only "raise" electrons if the radiation is at the correct frequency. 
