Question

This building...built by next month
1will built
2will have built
3will have been built
4will be building

Answer 1

This building will have been built by next month 
Future Perfect, т.к. будет построено к определенному моменту.
+старадательный залог, действие над объектом совершается: to be+3 форма глагола

will+have+to be+3 форма глагола