ZOHO CRM has five versions (Free, Standard,Professional, Enterprise, CRM Plus)

a) If I want to use ZohoCRM such that, every enquiry in my website will direct to Zoho as lead and Zoho will then automatically send an acknowledgement email to customer, which version should I buy

b) If I want to use Zoho CRM that whenever a person is assigned (manually or automatically)  any task in CRM pipeline, she gets an email in her office email account, which version should I buy

c) If I want Zoho CRM to hold my accounts information, invoicing for client and also accounts for my suppliers, which version should I buy?

It would be great if you individually answer these questions. I appreciate your help greatly. I hope I can be part of Zoho as soon as I get my doubts clarified. Thanks again for helping me.