Yes, you can have more than one materialized view on a table. You can even have the different materialized views have the same query, just using different names, and it will work as well.
As to the number of rows possible using materialized view, I don't think there is a limit just because it is a materialized view. The only limits posed (I believe, correct me if I'm wrong) are that of space.... run out of space to store the table, run out of rows you can add. Remember, a materialized view has similar properties to a regular table.