My question is regarding the cleanliness of dog. I have always heard from parents and grandparents that dog are considered as unpure similarly to pigs. I have always followed this but in recent time the activity of fellow muslims with dogs (caring, playing, kissing etc) specially the millennials made me to ask this question.
Are dogs impure and untouchable similar to pigs?

Yes Dog is najis but Najasat is only transferred through wetness, either ones body is wet, or the dog is wet, or it is the saliva from the dog.

In all other cases, najasat will not be transferred, however, one cannot do salaah with the clothes which has dog hair on it.