how do i get taskbar freeze on desktop which appear when clicking window button on keyboard on keyboard
You have not provided much info so I am guessing.
What you call a taskbar freeze may be the activities favorites menu across the bottom of the screen with gnome 40 on fedora 34.
If it is then the esc key will turn it off and return to the desktop. The window key is designed to display that and window+A gives all the activities menu items.
sorry for low info,
this yellow marked bar, which appears on ubuntu on left side by default on desktop i tried fedora 34 gnome 40 it was there when i press windows key on keyboard.
i want it to be there on desktop by default can i do that on stock gnome?
(im not sure what it called Sorry for that)
If by freeze you mean stay on the screen all the time, you can use an extension for that. Specifically, dash-to-panel.
That bar is the activities favorites menu. Gnome has never had it displayed constantly in 40.x and I never saw it displayed constantly in gnome 3.
With fedora 34 the gnome extensions are now managed by gnome-extensions-app so you can install that and possibly set it to be constantly displayed.