rahul.mane91 - dynamic playlists have no limit, you can call dynamic/next as many times as you want to get a song. Note that sometimes we may run out of songs depending on how constrained your playlist is. If you are creating static playlists, then the limit is 100 songs.
All of the playlist parameters are described in detail in the docs that are here:
http://developer.echonest.com/docs/v4/standard.html#static
Paul