Handling environments using .env

I can't make it work for me too.
I didn't understand the solution to change to development mode.
I opened the env file and changed to:

Code:

#--------------------------------------------------------------------
# ENVIRONMENT
#--------------------------------------------------------------------

# CI_ENVIRONMENT = production
CI_ENVIRONMENT = development

But when error occurs, it shows me the Whoops message.
The documentation says that the only change that we have to do is in .env file...

And I couldn't find no SetEnv on the .htaccess files, inside public and inside app.