Hallowtide is a Christian festival.
Traditional Halloween practice includes divination and necromancy
No they do not. That's a modern take on it from ideas from Victorians on pre-Christian practices that developed into wider cultures over the decades and influenced by other cultural practices on connecting with the dead.
Since back to the early churches there are writings on the importance of honouring and remembering the dead, particularly in the early church the importance of remember martyrs. Traditional practices involve remember those who've died and the good they've done, lighting candles or incense, having images of family and for some saints in preparations for All Saints and All Souls Day.
My family does Día de Muertos, a fusion of Christian and polytheistic traditions, so we add in marigolds, dressing as skeletons that we will one day be, handing out treats to others, making the foods our loved ones like, playing music and a lot of discussions around those who have died and our own feelings on dying, death, and mortality in preparation from All Hallows' Eve through to the evening of the second when we take the marigolds to a local river & on the 3rd, clean up for the year.