Signup forms behaviour : Same email & multiple submissions

Signup forms behaviour : Same email & multiple submissions

My use case is that I have a signup form (FormA) that I use in several places on my website, with a hidden field so I can see where the contact has been made from. I also have a couple of other signup forms (FormB and FormC) that slight differences. 
All three use the same journey so that information is sent to my CRM (via Zoho Flow)

I have had the use case that a potential client has filled in several forms - but only one ends up coming through the journey>Flow. I have 'Allow re-entry of contacts' with Open Trigger enabled.
  1. Can an identical email address progress through a journey multiple times in close timing?
  2. How long does it take for a contact to be recognised as a new contact?
    1. I made another test after 30 minutes and it didn't register as a new contact

This is the test submission I made, three contacts with the same email address, but different messages