Data-driven, Dynamic, and Interactive Web Application Architecture and Software Platform?

Planning to start a data-driven, dynamic, responsive, and interactive matrimonial Site in an Asian Country:

• With mobile apps for Android, iOS, and Windows phone
• Every user will have a profile page containing 1-3 images; detailed personal information
• It will have live chat facility for text, voice, and video
• Linking emails and messages to their personal emails and mobiles
• Push notifications
• Mobile/email/site approval for contact view
• Simple shopping cart and payment gateway (Paypal, Credit card, Debit card, or Direct from bank)
• Dynamic, quick, and easy window Search facility
• Third-party economy hosting and open source software
• Expecting thousands of active users shortly
• So, it will have large data and traffic; need high speed, security, scalability, and ease of use

I am thinking of using Python/ MongoDB/ Linux-Ubuntu

(1) Should I do it with

• Python/MongoDB/Ubuntu, OR
• Java/MySQL/Ubuntu, OR
• PHP/MySQL/Ubuntu?

(2) What should be the architecture? And what are the details of software/tools required at each layer?

1. Presentation Layer:
2. API:
3. Business Layer:
4. Data Access layer:
5. Resource Tier:
6. Data base:
7. Server (For caching):
8. Web server:
9. Servlet Engine:

(3) Am I missing anything?