Finally...

When I executed from sqlplus i've done it by
sqlplus username/password@sid @script.sql <- works

In PLSQL Developer i run CODE from script.sql <- not working.

Turned out that the problem is in coding.

utl_http.set_header(l_http_request, 'Content-Type', 'application/json; charset=utf-8');

when I changed it to

    utl_http.set_header(l_http_request, 'Content-Type', 'application/json; charset=WINDOWS-1250');

It works. I do not know why - could SQLPlus changing by default file coding? Most important thing that this is working.
Closed.
God is great!