Help asked with creating menu with PP vba

Having done a medium sized app with Excel vba I now started with PP and discovering that Google has much less to offer for the latter :-( Already tried a lot and a few things work, more or less, but it doesn't feel if I have a grip on the stuff (yet).

So I created a 1 slide presentation with on it 20 shapes each having a macro p?? as their action (where 01 <= ?? <= 20).

Each p?? macro must be able to invoke another (each a different one) presentation and run it immediately (hiding the 1 slide presentation).

Question 1: how can I do this?

Also each invoked presentation should exit itself when some exit button is pressed, makibg the single slide pp visible again.

Question 2: how can that be done?

Question 3: or would it be better to start first pp, then load all 20 other pp's and then dynamically switch between those? Maybe this would be too expensive memory wise?

Question 4: if answer to 3 is that that is a viable option, how can that be done?

Last but not least: could you point me to docs explaining at the right abstraction level how vba for pp works?

Thanks for any help.