Under Section 30 of the Indian Contract Act, 1872, an agreement by way of wager is:

Correct. Section 30 of the Indian Contract Act, 1872 expressly declares that 'Agreements by way of wager are void; and no suit shall be brought for recovering anything alleged to be won on any wager, or entrusted to any person to abide the result of any game or other uncertain event on which any wager is made.'

Incorrect. A wagering agreement is not voidable at the option of one party; it is void ab initio under Section 30 of the Indian Contract Act, 1872.

Section 30 declares wagers void. Its horse-racing proviso concerns qualifying subscriptions or contributions towards race prizes.

Incorrect. As held by the Supreme Court in Gherulal Parakh v. Mahadeodas Maiya, AIR 1959 SC 781, under Section 30 of the central Indian Contract Act, 1872, a wagering agreement is void and unenforceable, though not 'forbidden by law' or illegal per se under Section 23 (hence collateral transactions are not tainted under the central Act).