Starting with Hive 0.14, you don't need to specify Avro schema. It can be interpreted by Hive (Avto Serde). Adding a new column is also supported by a simple "ALTER TABLE ADD COLUMN <column name type>". More details on this link.
Changing column name is simple since it only changes the metadata.
//change column a's name to a1.
ALTER TABLE test_change CHANGE a a1 INT;
Replace column lets you drop a column but I am not sure if its Avro is supported. According to the documentation in