Let me answer your question one after another,
1) Thai is the starting month in the tamil calendar like January hence The first of thai is celebrated as a new year in Tamil culture
2) Yes we do celebrate four days of pongal
BHOGI- The day people used to Fire their old waste belongings and buy a new one instead, to welcome the upcoming new year on the next day
THAI 1- Tamil new year when people used to prepare pongal (rice +milk+nuts+ Brown sugar)
MATTU PONGAL- This day is dedicated for the cattle especially the cow where people used to decorate their cows and in some places they tie a bag in their neck and will make it roam around the village any one in the village who can remove that bag can take it(the bag not the cow) home.
KANUM PONGAL- In this day people usually go out to see their relatives. especially the brothers used to gift some thing to their sisters who got married depending up on their wealth.
3)I am very sure about celebrating pongal with the next generation. But the we celebrate it may defer depending up on the changes in our environment and surroundings even nowadays people in the city are not celebrating it when compared to the people from remote areas/ village.
There are several traditions in India which are interesting hence there are lots of diversities over here regarding religion, customs, culture, geographical areas. You can find lots and lots of interesting stuffs If you keep on exploring.