Director appointment giving back dated effect???

yes you can apply for the DIN now and can make good the defaulk  by filing form from back dates.Back date filing will incur additional fees.

Yes DIN can be taken as on date and you have to file DIN 3 as well.

You have to take DIN for all the directors. Also you have to apply for digital signature of one director for efiling.

As per MCA 21, every person who is a director of the company is required to apply for DIN and to file DIN 2 with the Company after the approval of DIN. Where the company will inform the ROC that the person is a director of such company by filing DIN 3. The directors may not be interested in carrying on the operation in 2007 so may not have applied for DIN. But now when they are intended to carry on the activities, ther are to apply DIN, File DIN 2 and simultaneously DIN 3 by the company. After which the company may proceed to file its accounts and returns with the ROC.