Android Application ID
You can get this ID in your AdMob panel, usually 1 Application ID can contain several Ads ID
IOS Application ID
I have no idea about IOS, never play aroud in that fancy stuff :) sorry cant help..
maybe you can just googling about it :)
I am not so sure about this, maybe something related to IOS Application ID.
Note : AdMob also provide Publisher ID, but somehow I think it doesnt needed to define in current MobileAdvert plugins. Maybe will implemented in future ?
Actually there is a lot of similar thread that discuss about MobileAdvert, maybe you can search about it ? :) Good luck..