How does the blockchain recognize a cheater manipulating the blockchain?

Let's say we have 100 blocks. A miner x intends to manipulate block 90. Therefore, he must recalculate the hash for block 90. Subsequently, he must also recalculate the hash values ​​for block 91-100.
Correct me if I speak pointlessly here.

So how can all the other miners discover that the miner is cheating x? And what happens to Bergmann x if he gets caught?

How to avoid manipulating the checkbox for users in Contact Form 7?

Sometimes we have to specify another option with the plugin CF7 via checkbox. For example, the dinner you have to reserve.

  • (A) Dinner for the 1st of April
  • (B) Dinner for the 2nd of April
  • (C) Dinner for the 3rd of April

If option (A) is full, we assume that we webmasters have a maximum capacity of 10 people. Option (A) is then manually removed.

But what happens in these different situations:

  • Some users have opened a page of your form and it will not be closed. This means that he can reserve more for the option (A) as he wishes.
  • Some users can change the value of the enabled option from any tool, such as Firebug, because they know the closed value (A). This option can therefore be marked for any user who knows this.

So the question is how to avoid these situations.
Why do not we sometimes get mails with some enabled options after removing an option?

Many Thanks,

c – manipulating a structure

The problem must be in another area of ​​the code, apparently the attribute seems to be set correctly. I assume your problem is different, but to answer the question simply use the "." (Dot) to access the desired item and the assignment operator "=" to assign the value.

Of course you need to create a "variable" to assign the actual value of a player in memory, in my case p1.

Here is an example:

#include 

using namespace std;

struct dataplayer {int life; int fitting; int weapon; int level};

int main ()
{
cout << "define life  n";

// your player
Data layer p1;

p1.life = 100;

cout << p1.vida;

Return 0;
}

You can test this code here:

https://www.onlinegdb.com/online_c++_compiler

Note: I too am not clear and I am tired. If you encode in c or c ++, I recommend you to choose one.