In exploration why "i" is not changing ?

I am not very familiar with loops so to understand it I ran exploration after that so I can understand how the values changes after each bar.

myema[ 0 ] = Close[ 0 ]; 
for( i = 1; i < BarCount-1; i++ ) 
{ 
    myema[ i ] = 0.1 * Close[ i ] + 0.9 * myema[ i - 1 ]; 
    
    }
Plot(i,"i",colorWhite);
Filter =1 ;   
AddColumn(myema,"myema",1.22);
AddColumn(i,"i",1.22);
AddColumn(Close,"Close",1.22);
AddColumn(BarCount,"BarCount",1.22);

In the exploration, the value of "i" is fixed at 2464. I was expecting it to be 1 on the first bar and then increasing 1 by 1.

Please guide me

A must-read portion of the manual:
http://www.amibroker.com/guide/h_understandafl.html

Your i variable is scalar, not array, so it represents single value (the last value as the loop has finished).

See also: How do I debug my formula?

You Plot i outside loop ( after } ) , that why you only see the last one.
Anyway Plot is not a good way to debug variables inside a loop.