Service tax credit

yes, you can take the credit of Service tax paid by us on Security Services or consultancy or any other service

Yes you can claim the credit. Please refer to the input tax credit definition in the cenvat credit rules

Security is allowed as credit. Consultancy if directly relatable to your business, may be admissible. But if you are providing non-taxable service , apportioning may be required undre Rule 6(3A ) of CCR.