Who will be held liable for payment of tax, interest or penalty after the death of the taxable person

In terms of Section 93(1) of the CGST Act, 2017, after the death of the taxable person, the tax, interest or penalty remaining unpaid either determined before the death or otherwise, shall be recovered in the following manner:
1. if a business carried on by the person is continued after his death by his legal representative or any other person, such legal representative or other person, shall be liable to pay tax, interest or penalty due from such person under this Act; and
2. if the business carried on by the person is discontinued, whether before or after his death, his legal representative shall be liable to pay, out of the estate of the deceased, to the extent to which the estate is capable of meeting the charge, the tax, interest or penalty due from such person under this Act.

(ICAI FAQ PUBLICATIONS 06-09-2017 Special provisions regarding liability to pay tax, interest or penalty in certain cases: FAQ NO. 15)

Whether the director of a private limited company is liable for the payment of tax in respect of the supply made by or to such private company

Yes. Every director of the private company during the period for which. tax, interest or penalty due in respect of any supply of goods or services or both, is not recovered shall jointly and severally be liable for the payment of such tax, interest or penalty, unless he proves that the non-recovery cannot be attributed to any gross neglect, misfeasance or breach of duty on his part in relation to the affairs of the Company.

(ICAI FAQ PUBLICATIONS 06-09-2017 Liability of directors of private company : FAQ NO. 9)

Whether in an amalgamation, the companies shall be treated as separate entities for the period starting from effective date and ending on the date of order of the Court

Yes, for the purposes of this Act, the two or more companies amalgamated or merged in pursuance of an order of Court or of Tribunal or otherwise, shall be treated as distinct companies for the period up to the date of the said order and the registration certificates of the said companies shall be cancelled with effect from the date of the said order.

(ICAI FAQ PUBLICATIONS 06-09-2017 Liability in case of amalgamation /merger of Companies: FAQ NO. 6)