BuddyPress.org

I have one doubt. i got suggestion from someone for the installation of my 2 domains on a single database with diff prefixes. as i am using same hosting. for the 2 domains.

my major problem is

my main focus is to advertise my site all over the world. with their local languages.
so i am using their country name domains.
its the begining i am using yet 2 languages. english and portguese. as i am focusing mainly on brasil and india us as in brasil i can get many users for my site.

for brasil i am using one brasilian domain
and for other countries i am using 1 other domains right now. to remove data complexity i did this.

yet i want to support 2 languages only english and portguese

on one domain i am installing buddypress in enlish
and on other kindly suggest mein what i can do if i want to show site to users in their languge portuguese in brasil ????? suggest me ??? what i should do. please no WPML any other alternate or plugin .

and also one confusion as i want to use 1 database if user from brasil opened english domain will he able to login ?? i want that database should be unique only. even if i use 100 domains i want to use single database for 1 site. kindly tell me