I am fairly new, so bare with me.

So, my understanding is that you should put the screen in upside down and backwards. (if you were looking through the lens hole).
Is this design specific related to all the other media that the image has to go through (mirrors, fresnels lenses?
and what are the advantages/disadvantages?

Does this orientation change with design changes?

Thanks.

Different designs require the LCD to be installed in different orientations. Check my tweaks topic linked in my signature line for an explanation that may help and also check the wiki. It'll all come together the more you think about it.

i am using irorate, a free program to rotate the screen upside down.

works fine.