Short answers, pulled from the story.
Constantine was born on the 27th of February 272 in Naissus, a city in the province of Moesia Superior, now known as Niš in Serbia. His father was a Roman army officer of Illyrian or Thracian origin, and his mother Helena was a Greek woman of low social standing, possibly from Drepanum in Bithynia.
The Edict of Milan was an agreement reached in February 313 between Constantine and his co-emperor Licinius that granted full religious tolerance to all faiths across the Roman Empire, legalised Christianity, and restored property seized from Christians during the earlier persecutions. Constantine also convened the First Council of Nicaea in 325, commissioned the Church of the Holy Sepulchre in Jerusalem, and financially supported the church through tax exemptions and basilica construction.
On the 28th of October 312, Constantine's cavalry broke Maxentius' cavalry on the first charge, while his infantry drove Maxentius' foot soldiers into the Tiber River. Maxentius drowned when he was pushed from a temporary boat bridge by the mass of his own retreating soldiers. Constantine entered Rome the following day.
Constantine chose the Greek city of Byzantium for its strategic position controlling the Bosphorus shipping lanes and providing access to defend Asia, Egypt, and the Danube frontier. The city was formally dedicated on the 11th of May 330 and renamed Constantinopolis. It served as the capital of the Roman and later Byzantine Empire for more than a thousand years, and is now the city of Istanbul in Turkey.
The solidus was a new gold coin Constantine introduced to stabilise the Roman economy after decades of inflation caused by debased currency. Seventy-two solidi equalled one pound of gold. The coin became the monetary standard for Byzantine and European economies for more than a thousand years after its introduction.
Constantine had Crispus killed by cold poison at Pola, modern Pula in Croatia, sometime between the 15th of May and the 17th of June 326, and had Fausta killed in an overheated bath in July of that year. Both names were subsequently erased from public records and inscriptions. No contemporary source provides a definitive explanation for either execution, and the few later sources that speculate are considered unreliable.