Avro cycle support

My group is considering using Avro and we had some questions that I am hoping someone might have some insight into.

1. Is there a plan to add cycle support to Avro? I saw this ticket: https://issues.apache.org/jira/browse/AVRO-695. But it hasn't been worked on since 1/2011.
2. Why does Avro handle cyclical schema's but not cyclical objects?
3. Does anyone know when non-string map keys will be available (i.e. ticket https://issues.apache.org/jira/browse/AVRO-680)?
4. How does Avro handle inheritance in lists? For example: List<BaseClass> storing derived class objects?

Thanks for your help.

_bernhard