How can we test run/compile a php code from modx control panel ?

hi is there anybody u can provide me paid/free consultancy for teaching little bit of using modx

Can we use modx for very large php programs. if yes then we should use plugins or snippets for this purpose ?
How can we test run/compile a php code from modx control panel ?
why there is no navigation & templates for modx ?

Please don’t double post.