- poke faces (Alt-p) doesn't exist
It's in the Face menu, so either select the 'Face' menu dropdown from the viewport header menus, or press Ctrl-F, or press W (context menu) while you have some faces selected.You can also just right click on the "Poke Faces" menu item, click "Assign Shortcut" and press Alt-P.
- the selection behaviour (A doesn't seem to deselect any more)
Alt-A clears the selection. - shift-G doesn't work
Shift-G does grouped selections, I think this is the same as in 2.79. - W doesn't open a menu any more.
The specials menu has gone, replaced by a context-sensitive menu (what a right click might pop up in most apps) So "Poke Faces" is here when faces are selected. - Shift-tab doesn't change vertex/face/line selection mode any more.
Ctrl-1, Ctrl-2, Ctrl-3.