Several customizing issues

Hi

I’ve got several questions. I’ll write on here in order to speed up response. I hope I do it in the right way.
My blog is japon-secreto.com

-Custom post layout:
Can I show every post with a custom layout (the same custom layour for ALL of them)?
for example: the post and some other widgets as in my home page.

-Logo on the menu bar
Can I show my logo as in twitter site? I mean to show my logo (small) on the menu bar when I scroll down.

-Is it possible to show more than 4 posts in Post loop?
By the way “build posts query” button won’t work.

-No sidebar in tag/calendar/category view
Can i do it? how?

Thank you so much for your assistance