For example I know that 2018 is the hexadecimal equivalent of left single quotation mark, and I have the following questions:
I know I can list the Unicode names using C-x 8 RET TAB, but this list doesn't show the equivalent codes (preferably in decimal).
@paulie4 pointed out command describe-char.
Command apropos-char from library apu.el prompts you for an apropos pattern to match against Unicode character names. The pattern is a regexp or parts of the names to match. Then it shows you the characters, their names, and their code points (decimal and hex). See Apropos Unicode.
You can use M-x describe-char to get info on the character under your cursor (see http://ergoemacs.org/emacs/emacs_n_unicode.html). Since you know C-x 8 RET can be used to enter a Unicode character using its name, I think that should answer your first question, but I do not know if there's a way to list them all by code points.
Note: I just looked at the help for insert-char, and it says you can enter the code point to insert using decimal by prefixing it with #10r :
- As a code point with a radix specified with #, e.g. #o21430 (octal), #x2318 (hex), or #10r8984 (decimal).
C-u C-x = is the standard key binding to show you the describe-char information (and plain C-x = shows some minimal details in the echo area).
2018is the hexadecimal value for LEFT SINGLE QUOTATION MARK, not the decimal value. Are you sure your question meets your actual requirements?