dynamic database

hello,
1) can i create a dynamic database in postgresql 7.0 ? if so how
many number of databases (maximum number of databases) a postgresql 7.0
installation support ?
2)can i restrict the size of a database while creating it ? later
sometime can i change
the same ?
3) can i restrict the sizeof a table while creating it ? can i change it
later sometime ?

i am in immediate need of your help . please reply as soon as possible ?

thanx in advance .