Does a divorce issued by a man married to his first wife—on official court papers—under a name other than his real name and with the intention of not divorcing, take effect, and does he need a new Islamic marriage contract to return to his first wife?

If the divorce was merely writing without uttering, or uttering with an ambiguous phrase without intention, then nothing is binding on you, and the wife remains under your marital bond and does not require a new contract. However, if you explicitly uttered a clear divorce, then it is effective even if you did not intend it, and the wife is not permissible for you except with a new contract, provided that this divorce does not complete the three divorce pronouncements.