How to add more functinalty to our forms with our own scripts and create plug-ins

Hi all,

Please assist me on:

1)      How can we use our own code to add more functionality to form?

2)      Is this possible to create a custom plug-in and add in the plug-in list which can be configured to use in a form whenever required?

3)      Can we dynamically hide the form fields, form sections at specific workflow levels?

I will appreciate if you can share other areas where it is possible to add our own code for adding more functionality.

Best Regards,

Amarjit.