Jason Finnegan, 19, with an address at Henrietta Place, Dublin 1, pleaded guilty to more than 30 charges.
He was handed sentences totalling six months suspended on the condition he remains on probation supervision for two years.
He was aged 17 at the time of the crimes but had reached adulthood by the time his case was finalised today at the Dublin Children’s Court.
Judge Paul Kelly noted he had completed a seven-week placement in a residential addiction treatment centre and accepted assistance from a range of services.
The defence had said his offending was also attributable to education problems, drugs and the murder of his brother.
He had a supportive mother, no prior convictions and the offences were confined to 2019 and early last year, his solicitor John Shanley told the court in a mitigation plea.
Finnegan, who previously lived at Mary Aikenhead House in Dublin 8, is also awaiting sentencing for other violent offences.
Judge Kelly noted reports showed the youth had engaged with the Probation Service and has been offered psychological counselling, was in a training course and is due to continue his drug rehabilitation work.
The court heard earlier that the boy turned up at the woman’s flat in south Dublin on a date in February 2020. He was already known to her.
Garda Aelish McBrien said the youth produced a large knife with a 10-inch blade in front of her and her frightened two-year-old daughter.
He threatened to burn her flat.
Two days later, the same knife was seized from him at another location in the city. Garda McBrien handed into court a photo of the weapon.
The woman suffered a minor injury to one of her fingers. This incident resulted in charges for assault, threatening to cause damage, and brandishing a weapon.
He smashed in windows at another woman's home after rowing with her partner on a different date.
The youth also pleaded guilty to possessing drugs for sale or supply in south inner city Dublin on three dates in February last year.
Gardai caught him with about €1,900 worth of drugs – a combination of heroin and crack cocaine and a small quantity of cannabis. He had tried to abscond from gardai and threw a package with the drugs into a garden.
He was caught on another date with €250 worth of crack, heroin with a street value of €3,670, and €365 in cash.
Garda McBrien told Judge Kelly the teenager attempted to discard packages containing €1620 worth of heroin and €140 of cannabis after gardai approached him on the third occasion.
He also had had a cannabis addiction but had stopped using other types of drugs. He also admitted driving without a licence or insurance on three occasions, resulting in being banned from driving for four years.
Earlier this month, Stephen Penrose was convicted of the brutal murder of his Jason's brother, Philip Finnegan, in Rahin Woods near Edenderry on August 10, 2016.
Penrose lured his pal to the woods before stabbing him 13 times in a frenzied attack. Penrose then made attempts to cut up his friend’s body and burn it before dumping his victim in a shallow grave.
His decapitated remains were found weeks later by a dog walker.