Few Simple Questions

HI

how can i get user ip, who can only connect by tcp/ip , for example in
plpgsql function .  ??

how can declare and define my own variables in each connect to db, and
read it / or change it in plpgsql function ?

is possible to create this same name of users in one postmaster but in
different db ?

how to change default grant to created objects, (tables ,functions, etc) ?

where can i change max length of function's name ? its can be only in one
place ?

how can i return more then 1 row in one time in function with SETOF
same_type; (plpgsql) like : RETURN NEXT SELECT f FROM BIG_TABLE ;

how to disallow user to create anything, user for example can select from
same function. this user also can not see others databases and objects in
actual db .. etc  ( it should be default ?? ) ?

how set default value of function's args.

Can someone help me with this problems ?

thx :>

bye
 ivan