I had download unity, can I create games free for Android and then buy the licese when I am I want to publish?
I haven't gotten into this, but I'm pretty sure the answer is no for the Android specific parts. You can still make your game like it's for PC/Mac and then change the inputs when you get the Android license, though.
You can't really effectively create a game without a device to test it on properly. (As you're working on it, not later after you've done a ton of work only to discover that it won't run well.) So, no.
you can try the android pro trial version,which is for 1 month and when you are over with your game you can purchase the licence