Button activity

1. You can use a!startprocesslink() in which another interface will be plugged into the "user input task". Make sure to use process Channing.

2. You can simply use the process model and on every action of the button you can change the flow of the model.

-@harshjan, that sounds complicated to me. besides you cannot use links in buttons if you dont create a button styled cardlayout
In general there are two main paths in my opinion: 

1.) you submit the form and go to the next form (process chaning)
2.) hide the not needed parts for your form by setting the visibility conditions (showWhen parameter)  - perhaps in connection with a "WriteTodatstore" smartservice - but not necessarily as a total submit in the end might sufficient.