for 1 question,

I use M-x describe-font, press Enter after mini buffer shows: Font
name(default current choice for ASCII chars).
Get the following info:

name (opened by):
-DAMA-Ubuntu-normal-normal-normal-*-17-*-*-*-*-0-iso10646-1
       full name:
Ubuntu:pixelsize=17:foundry=DAMA:weight=normal:slant=normal:width=normal:scalable=true
            size: 17
          height: 19
 baseline-offset:  0
relative-compose:  0

Also try to evaluate the expression in eshell, get the same result.

~ $ (face-attribute 'default :font)
#<font-object "-DAMA-Ubuntu-normal-normal-normal-*-17-*-*-*-*-0-iso10646-1">


for 2 question, please see the following screenshot, after C-u C-x RET,
mini buffer shows C-u C-x RET-
[image: Inline image 1]


-- 
Best Regards!
Dean Chen

+86 18652581062
GraphSQL Inc.