Questions On Printing Techniques Thailand Revenue Stamps

I read thru several of the threads in this forum on printing techniques, I must say I am now more confused than before.
Maybe some of my collector colleagues have some time/ patience to explain my questions in some details.

Around 1885, Thailand issued agriculture revenue stamps. Printed maybe in France, in sheets of 100 (10X10) mono-color.



originally these stamps were printed with 2mm spacing between the printed areas of the stamps. The blue border line thin and straight.
Later these stamps appeared with 3mm spacing between the printed areas, also the blue border lines are thicker and not completely straight.
But in this later retouched(?) printing the various stamps on the sheet have different redrawn lines with different imperfect areas.

Questions
1. From the scans is it clear what printing technique was used for those stamps?
2. How did they transfer 100 similar images into 1 plate? Via master die?
3. To have a plate with spacing between stamps of 2 or 3 mm, complete new printing plates had to be made?
4. Why does the printing plates with 3mm spacing between the stamps have different looking frames for each stamp? Why not retouch the master die if needed so all stamps look the same?

Thanks so much, please ask questions if my story is not clear

Hi Jos,
I am not aufait with French Printers,
Looks like lithography to me.

Here is a basic 101 on Lithography
BiB : "Collecting Postage Stamps" L.N & M Williams 1950




Here is the Western Australian Lithographic Stone
Look at the far right block of stamps
End column, 5 stamps down.........

That is the famous "Inverted frame" of the Black Swan
(click image to enlarge)

Rod, thanks a lot. The explanation on lithography is very clear.
The revenue stamps shown in my post are very smooth on front and back, indicating they are lithographed stamps.

I also understand now how they make multiple similar images on a stone or plate with the frame lines manually drawn.
Now I also understand that in my first post the stamps with 3mm spacing is a separate plate and the frame lines are less carefully drawn as in the first printings where the spacing is only 2mm. That all the frames look different has to do with the manual drawing provess, nothing with retouch.

Thanks

Cheers Jos,
It took me some time to gradually feel more confident, picking
Lithography over letterpress.
Letterpress, usually has "ink pull" in the corners of frames

Anyone wanting to practice detection should try the 1945 Argentina "San Martins" they nearly drove me batty