Why is the signal always entered into minus port in inverting op-amp?
Your assumption "output voltage value is same either if I connect input signal into + port or if I connect input signal into - port." is wrong.

Your left circuit does not work as a linear amplifier.
Iuses positive Feedback. Depending on the input voltage it saturates close to one of the supply voltages (not shown in your diagramms; probably +10V and -10V; in your case it saturates to -10V).

So the left circuit is not a circuit that makes sense to compare to the right one.
It could be useful, though, as a Schmitt-Trigger (i.e. comparator with hysteresis).

If you compare two (amplifier) circuits, it is not enough to compare input and output voltages of just one instance (in your case \$V_{in}\$=1V, \$V_{out}\$=-10V) but of the whole operating range.
If you compared the behaviour of the circuits at other voltages (e.g. \$V_{in}\$=0.5V), you'd have found that they are not equivalent.