What is the size of DB in Postgresql??

Hello,

I have 2 questions:
1) What is th max size of database we can create in Postegrsql?
2) Suppose I have two simular  databases: mydb1, mydb2 (containig the
same number of table, ...etc.), how I can copy the contents of mydb1
into mydb2? if mydb2 is on a remote machine, how I can do this?

Thanks