Is there a primer for people who never played the original game? Believe it or not back + low kick isn't really all that an intuitive way to do a foot sweep. What about the kill moves? Any suggestions about how to map the keys to a keyboard?

I own the three games on GOG for years, but I'm still noob. There's even no manual included in the GOG release.

Hello gamer1214,
There's a trick to activate the cheat mode by pressing a key instead of having to type "AICULEDSULL" every time you start up.
You just follow the instructions in Hulk1313's post on "MK 2 more Kredits?" https://www.gog.com/forum/mortal_kombat/mk_2_more_kredits
I suggest using the HEX-Editor with NotePad++ which is easy to use.

Download NotePad++ : https://notepad-plus-plus.org/
Download nppPluginManager : https://github.com/bruderstein/nppPluginManager/releases
Download HEX-Editor : https://github.com/chcg/NPP_HexEdit/releases

The instructions :
NotePad++ : https://www.youtube.com/watch?v=f7ppjrzGONM
nppPluginManager : https://www.youtube.com/watch?v=bOJTxmfmP8g
HEX-Editor : https://community.notepad-plus-plus.org/topic/17459/why-there-is-no-new-hexeditor-now

Translated with DeepL (free version)

Awesome, didn't know that!

convention
JP - jump-punch
JK - jump kick
1 - low punch
2 - high punch
3 - low kick
4 - high kick
B - block
R - run
right arrow means forward

inscriptions
e.up - move available only when opponent is in the air (either jumping or has been hit into the air)
air - move can be done only in the air (while jumping)
a.air - move available both on ground and in the air
any - finisher can be performed from any distance
cls - closeup distance
swp - sweep distance (length of a leg)
o.swp - just slightly farther than swp (out of sweep)
hlf/mid - exactly half of the screen (middle distance)
far - approximately 2/3rds of screen width
scr - FULL screen width

stage fatalities can only be done on maps with pits
"The Pit" map itself does not require any sequence and a simple uppercut will do fatality
others require a sequence being dialed, followed by an upeprcut
animality is only done after Mercy (special hotkey required, don't remember what)

notation
←+2 - press two buttons simultaneously
4... - tap button rapidly
[←→] - optionally press either of these buttons
hold 2 →→* means keep holding 2, then briefly press the sequence, then release the being-held button

missing distance data means it was lost
question mark ? means data is unknown or not confirmed

notice data has been restored from legacy notes, partially from photos, and therefore, is not 100% correct (particularly, some finisher distance data is controversial)

notice 4 characters from the roster can be switched to their legacy variants (such as Kano MK1); special hotkey must be used while in the roster screen