Short answers, pulled from the story.
Murus Romuli is Latin for "the Wall of Romulus", the name given to a wall built to protect the Palatine Hill in Rome. The Palatine is the centermost of the Seven Hills of Rome and one of the oldest parts of the city.
Tacitus describes Romulus ploughing a sacred furrow, the sulcus primigenius, starting from the Forum Boarium (marked later by the bronze Bull of Myron), running through the valleys around the Palatine, and ending at the Sacellum Larum. The path was marked with stone cippi, and the Ara Maxima of Hercules fell inside the furrow's boundary.
Remains of an early defensive wall were found on the north slope of the Palatine Hill in 1988. Archaeologists argued the find indicated Rome emerged as a dynamic society by at least the 7th and 6th centuries BC, earlier than previously calculated.
The earliest evidence of any settlement in the area dates to around 1000 BC. Large-scale organization is evidenced by the Esquiline Hill's necropolis and a clay and timber wall at the base of the Palatine Hill dating to the mid-8th century BC.
No. Archaeologist Rodolfo Lanciani argued the shape of the Palatine walls was trapezoid, not square, and that the name Roma Quadrata belonged to an altar in front of the Temple of Apollo rather than to the hilltop city. The surrounding valleys were also too waterlogged in Romulus's era for a founding furrow to have been ploughed through them.
Romulus is most often considered a figure of myth, but some scholars, including Andrea Carandini, have argued he was a real historical person. This view remains a minority position among researchers.