1) The unsold stock would not attract GST... Please refer to the transitional provisions... Section 142... Extract is as below:
"(11) (a) notwithstanding anything contained in section 12, no tax shall be payable on goods under this Act to the extent the tax was leviable on the said goods under the Value Added Tax Act of the State;
(b) notwithstanding anything contained in section 13, no tax shall be payable on services under this Act to the extent the tax was leviable on the said services under Chapter V of the Finance Act, 1994;"
2) Unsold stock cannot attract tax credit as no tax has been paid on such stock.
3) There is no grace period required because stock can be sold off any time after applying GST.