How to get all messages for today on VKontakte and / or classmates?

Question

In contact with

Actually, all messages are needed in order to analyze the statistics of the words used.
word: quantity
is better of course the messages themselves, but it will go like that.
data for any given day.

Answer 1

in VK is simple:
You get the rights to access messages
Then there are two options:
1) You receive all messages and write them to your database
2) You receive messages in a cycle until you reach the desired date.
well, you can probably write the processing algorithm yourself

Answer 2

how to get all messages? access restrictions?
How to get permissions to access messages?
of course, public messages are of interest ....
I think there will be hundreds of millions