What is RMD?
How come oKEY is like that and RKEY is a capital. What is different??
How do you undo 1 step?
For the second question, possible to distinguish O from 0 .
RMD should probably be RMB the right mouse button. Some commands require the capital letter ie. “d” is draw mode, shift d “D” is duplicate – however people usually write shift-d if the shift is required. In most stuff you read in tutorials etc. there is no difference between d-key and D-key.
GreyBeard
In Edit mode you can push Ukey to undo. Alt-U for undo history. Object mode Ctrl - Z to step back. Save often, and Save as after major changes = good practice. Enjoy!