security amount

Yes. While a normal taxable person does not have to make any deposit of money to obtain registration, a casual taxable person or a non-resident taxable person shall, at the time of submission of application for registration under sub-section (1) of section 19, make an advance deposit of tax in an amount equivalent to the estimated tax liability of such person for the period for which the registration is sought. If registration is to be extended beyond the initial period of ninety days, an advance additional amount of tax equivalent to the estimated tax liability is to be deposited for the period for which the extension beyond it is being sought.

Not declared yet, wait for final rates.

As per Model GST  law : a ‘taxable person’ is a person who carries on any business at any place in India and who is registered or required to be registered under the GST Act. 

Any person who engages in economic activity including trade and commerce is treated as taxable person.

While a person who occasionally supplies goods and/or services in a territory where GST is applicable but he does not have a fixed place/occassion of business. Such a person will be treated as a casual taxable person as per GST.

Casual taxable person may obtain a temporary registration for a period of 90 days (extendable for additional 90 days).