QR Codes as Booking Confirmations for Conference?

A client of mine is holding a conference and we have the task of creating a booking system for them. However they have requested that we use QR codes so that on the door, a person can simply present their QR code, be scanned, and boom! they are signed in.

QR Code weird alphanumeric group conversion

characters corresponding values
When converting something in an alphanumerical mode to a bitstream you first have to

Prevent my QRCode from being copied to another medium (paper/card, screen.. etc)

I want to make an app that reads QR code from places that I and only I have generated the code for.

How to download qr code with some text below

I have to download qr code with some name like i have to download whole view with qr code and text its downloading qr code but not the view with text this is what it’s downloading and second picture describe what i want to download.

How many bytes can I fit into a QR code, with low error correction?

I need to fit at least 300 bytes (or much much more) into a QR code and think I can do this by mapping each byte into the associated ISO/IEC 8859-1 character located here.

How many bytes can I fit into a QR code, with low error correction?

I need to fit at least 300 bytes (or much much more) into a QR code and think I can do this by mapping each byte into the associated ISO/IEC 8859-1 character located here.