Upgrading means more Space or Bandwidth (for data transfer).

10 POSTS = 50 MB Web Space/1000 MB Monthly Data Transfer
50 POSTS = 50 MB Web Space/5000 MB Monthly Data Transfer
100 POSTS = 60 MB Web Space/5500 MB Monthly Data Transfer
400 POSTS = 80 MB Web Space/6500 MB Monthly Data Transfer
800 POSTS = 100 MB Web Space/8000 MB Monthly Data Transfer.

PHP and Mysql are not available in Free hosting. You can use html, images, Flash and Java scripts with free hosting.