Unfortunately, there is no hotkey support anymore for the Alt+Space window menu. However, you have keyboard shortcuts for the most common actions. These do not require you to see the menu and reduce the effort to one single keystroke.
- Minimize: Super+h.
- Maximize: Super+up.
- Move: Alt+F7.
- Resize: Alt+F8.
- Close window: Alt+F4.
These key assignments can be changed in Settings - Keyboard.
Always on top: such keyboard combination is not defined by default, nor exposed through Settings - Keyboard. You still can define a key combination using dconf-editor, or a gsettings command. For example, to set Super+t for toggling the window on top, issue the command
gsettings set org.gnome.desktop.wm.keybindings always-on-top ['<Super>t']
Undo with the command
gsettings reset org.gnome.desktop.wm.keybindings always-on-top