complete guide to recaptcha

[Naimish_Dave]

Hi,

I want to implement reCaptcha on test landing page and i am following below reference url :

medium.com/@anulals/google-recaptcha-in-marketo-forms-b992fc30d000

My Questions as below : 

1. In this article one of the step is mentioned “Now we need to create a flow to perform operations like add to lead list or send emails etc”. May i know where we should create this?
2. That webhook and flow, when it will execute? is it at the time of before insert record in marketo?
3. In my marketo account already everything is configure, even marketo records are sync with salesforce so is it any specific action require for this? like i need to sync only those records which are non-spam record?
4. If i have implement on test landing page for testing purpose so is it impacted to existing marketo forms or existing setup?

Thanks in Advance...