I have see all answer of question, How do I set Developer Mode in Magento 2
All are good.
But suddenly i got another solution myself ,by directly change
MAGE_MODE value at
app/etc/ ) and here change current application mode from default to developer by
MAGE_MODE' => 'default' to
MAGE_MODE' => 'developer' .
and it been works.
But now my question is that this a good solution for change Application mode?.
Please put your views.