How to add a portal with access for customers?

How to add a portal with access for customers?

I know it is possible to add a portal for a kind of customer self service to Zoho CRM. For example I do want to send a link to the customer where he can check his address and change it, if the address has changed. But I do have a few questions:
  1. Is it possible to setup a login for each customer (using a password plus a custom field from the module which the customer has access to, i.e. Customer ID).
  2. And if the customer has changed the address can I add a verification step to the process, so that I can check the changes the customer made or is the changed address immediately transferred to the customer module?
  3. And is it possible to create custom QR codes for each customer containing the link to the customer portal plus the Customer ID? So he only has to fill in the password then. 

Thanks for help.