5. 4[ Decisions in certain cases to be according to Native law. In questions regarding succession, special property of females, betrothal, marriage, divorce, dower, adoption, guardianship, minority, bastardy, family relations, wills, legacies, gifts, partitions, or any religious usage or institution, the rule of decision shall be--
(a) any custom applicable to the parties concerned, which is not contrary to justice, equity or good conscience, and
has not been, by this or any other enactment, altered or abolished, and has not been declared to be void by any competent authority;
(b) the Muhammadan law, in cases where the parties are Muhammadans, and the Hindu law, in cases where the parties are Hindus, except in so far as such law has been altered or abolished by legislative enactment, or is opposed to the provisions of this Act, or has been modified by any such custom as is above referred to.]