What is the ruling on praying two rak'ahs before Maghrib and two rak'ahs before 'Isha at home? And must they be prayed between the Adhan and the Iqamah, or is it permissible to pray them at any time?

The two rak'ahs before Maghrib prayer are a confirmed Sunnah (definition). The Companions used to perform them in the presence of the Prophet, peace and blessings be upon him. He commanded them for whoever wished, saying: "Between every two calls [to prayer] is a prayer" - three times - "for whoever wishes." Their time is after the adhan (definition) and before the prayer. And two rak'ahs after the adhan of Isha are also Sunnah based on the same hadith (definition). Performing these two rak'ahs at home is permissible, as he said: "The best of a man's prayers is in his home, except for the obligatory prayers."