I don't know what is causing the difference between my interpolation of object and the on from tutorial that i follow, even though i have following every single step to the point of creating interpolation correctly.

How to fix this? Below is the picture of interpolations

It´s totally correct when I place same size (and shape over the screenshots) I got the exact same output:

Is the picture below inkscape version not the same as the above one? 

I wonder why inkscape develop the interpolation function to becomes like that? I mean isn't it more beautiful if the interpolation stay the same as in previous version, rather than making object getting bigger and bigger like in the new version? ( sorry for long comment) 

I took your screenshots as a blueprint to check the extension - and it just works. In comparison to the video screenshot you´re not having circles and the distance is closer; that´s why the objects are overlapping. The dialog in current 1.2 looks like this BTW:

So i can't make my objects to have interpolation of equal lengths in my version of inkscape, unlike in inkscape 1.2? 

I have no clue why you think it´s not possible. This is after your vid-screenshot in Inkscape 1.1.2: Equal distance of object´s midpoints.

Because i think there is no menu for split path into segmen of equal length, unlike in your picture of inkscape 1.2. Well at least i know it is possible, i just have to adjust its distance right? Because you say, it is what make my object's interpolation is overlapping

@earvinwilliams96,  Interpolation uses distance, not object size.

If you would like equal spacing between objects, the Align& Distribute dialog can be used.

@TylerDurden so i must manually set the spacing for object to be equal in length in my version of inkscape? 

The align & distribute dialog should be used after interpolate, if the spaces between objects need to be equal. (Not the distance center to center.)

http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Align.html

I finally find the solution, There is 2 solution,

First, you can make the horizontal gap between object equal by using the second from right top button of Distribute tool ( i have circled it with red colour)

Second, you can make object's spacing equal by making longer distance between first object and last object.

I have included the screenshot

Not a single word did you mention that you wanted equal spacing between instances; Interpolation can´t do that.

Oh, i am very sorry if i make you confused all this time, what i actually wanted to do is to make spacing equal. But i am too focused with the term " Interpolation" so i forget to tell you what i really want to ask you

Thank you for you @Polygon and @Tyler Durden for all of information you mention. I am sorry if i wasn't cleared with what i wanted

No worries. It was clear enough to help find a solution. 👍