1)How does a war work
The attacker may choose to move all purple tokens followed by the defending players in player order. After that a)the battle ends and continues on in the following year or b)player continues to take movement turn after that? a) or b) which is right?
When do we go back to normal worker placement phase after the war phase?
b) is right. The war goes on until either all the attacker's tokens are destroyed or three consecutive turns of war have happened without a battle.
how many times does the attacker moves before the war ends?
In a single turn,
attacker - defending players - attacker?
They go on like that until one of the above conditions is met.
Do you do war check every turn or only on the turn when there is no ongoing war ?
Every turn - there is never an ongoing war.
3)Can the numbers of defenders token move to the minor buildings exceed the maximum activations of that building?
Yes, I think so. I guess you would have to remove excess tokens on a building at the end of the war - i.e. you wouldn't have the option of leaving them on the city - or at least there would be no point in doing so.