HI I tend to use abbreviations...and until you get a better reply
WM=window manager
DE=desktop environment
TC32/64 the x86 or x86_64 distros of Tinycore Linux
GUI graphical user interface, a program that tends to run outside of the terminal, they can be launched from a terminal.
altho your Question names DE and desktop, it does not hurt to see what Linux users tend to expect but may not have on TC32 or TC64.
https://en.wikipedia.org/wiki/Comparison_of_X_window_managersCrudely put a DE is a WM with a suite of apps, normally they include
their own file manager, terminal, control panel (where applicable), media player
and often bundle their preferred web browser.
Now the desktop is what both the WM or DE must supply.
Crudely the desktop paints things onto your monitor and depending on the choice may include:
inbuilt tray panel quick launch bars
menu support
icon support
notify support where applicable
background paint or wallpaper support
and interactions with input and output devices
Not all apply.
Third party apps like wbar can act as a quick launch bar for GUI apps
2) The kernel is never responsible for supplying you with a desktop. It may have foundations or in window speak driver support for the graphical engine that underpins a WM or DE
These engines are libX, Xorg or Wayland
3)
If I want it to support both the graphical interface program, don't want to use the desktop (but use the terminal to replace it) what should I do?
Someone with better skills may know what you mean but let me give you my answer.
Some apps can be run outside a graphical environment.
Click the exit button and choose exit to prompt.
a number of apps can run from there. It is sometimes called the console.
But the desktop is not running.
examples include nano feh and mc
(b) If you actually mean you want a terminal based app to replace a GUI then please name the ones you want to replace please.
eg there are terminal based media players eg mpg124, aplay, arecord etc
terminal based text editors ....eg nano
terminal based file managers eg mc
good luck