Here are the answers

1. Where does the New Year’s Day concept come from?
It stems from an ancient Roman custom, the feast of the Roman god Janus. This is also where the name for the month of January comes from, since Janus was depicted as having two opposite faces. One face looked back into the past, and the other peered forward to the future. His name derived from the Latin word ianua, which meant "door" and showed his authority over thresholds, including those between years, months, days, and even states of being.
Likewise, on January 1, we look back at the year that just ended and forward to the new year ahead.
To celebrate the new year, the Romans also made promises to Janus. The tradition of New Year’s resolutions stems from this ancient custom.

2. What New Year's practice is traditional in Scotland and Isle of Mann?
I was looking for first footing, but also accepted Hogmanay
First Footing : The first person through the door on the New Year's Day may set the tone for the coming months. In Scotland, the Isle of Man and some other parts of Northern England, the "first footer," as it was called, was extremely important. Tradition in those parts of the world states to select a man who is tall and dark (as a protection against Vikings), who would come with simple gifts of coal, salt, shortbread and whisky, representing the basic needs of heat, food and drink.

3. How is new year celebrated in Spain?
New Year's Eve in Spain is called "Nochevieja" (it literally means Old Night). The tradition is to eat one grape at each stroke of midnight. Those who do it are promised good luck for the next year — if the rules are followed: "Eating one grape at each of midnight’s 12 clock chimes guarantees you a lucky year — if and only if you simultaneously ruminate on their significance"
"If you fail to conscientiously finish your grapes by the time the clock stops chiming, you’ll face misfortune in the new year."