When you say "how can I get page template info which I just chosen ?",
what do you mean?
Because you can see which template you choose by going to DESIGN tab, at the top you will see green background and on it "page template: ..pageTempalteName.."
you can go to Properties tab -> Template.
If you looking for some other way, you can use macros:
Hope this helps,
Adam @ 4Hilton