Itr submission for a professional- income more than 15 lacs

I have to file Income tax return for Fy 2011-2012. I income/receipts are more than 15 Lacs. Please see following queries:

1. What will be the last date for ITR-4, considerding income more than 15 lacs.

2. Do the Income/Bank Account need to be audited, as the income is more.

3. Till last year, income was less(5-6 Lacs), So i was to file my own. I have some expenditure in some types, & the submission/refund was successful. Should I file my ITR by my own or take services from a CA?

4. Please help, what other things are required now onwards?

5. Do i have to have a TAN also from this/next Year.

Any Expert, Please advice...

Regards