To determine the validity of the contract entered by an insane person during sanity:
1. Under Section 11 of the Indian Contract Act, 1872, a person of sound mind can enter into a contract, and a period of sanity qualifies as such a state.
2. If an insane person enters a contract during a lucid interval (period of sanity), the contract is considered valid, as per Section 12, unless proven otherwise.
3. It is not voidable, fraudulent, or void ab initio under these circumstances.
Therefore, the correct answer is (1) Valid contract.