The contract is Illegal contract and not just void. All Illegal contracts are void contracts but all void contracts are not Illegal. Also all the collateral contracts of an illegal contract are void whereas collateral contracts of void contracts are not necessarily void. This is the difference between void and illegal contracts.
Investment is the answer for the current account question, Investment is included in Capital a/c while current A/c includes transactions of revenue nature, Capital A/c includes transactions of Capital nature