Help a Newbie

ReadProcess memory isnt external ? because no have acess to process, is hidden and blocked.

hProcess [in]
A handle to the process memory to be modified. The handle must have PROCESS_VM_WRITE and PROCESS_VM_OPERATION access to the process.
lpBaseAddress [in]
A pointer to the base address in the specified process to which data is written. Before data transfer occurs, the system verifies that all data in the base address and memory of the specified size is accessible for write access, and if it is not accessible, the function fails.
lpBuffer [in]
A pointer to the buffer that contains data to be written in the address space of the specified process.
nSize [in]
The number of bytes to be written to the specified process.
lpNumberOfBytesWritten [out]
A pointer to a variable that receives the number of bytes transferred into the specified process. This parameter is optional. If lpNumberOfBytesWritten is NULL, the parameter is ignored.
Return value

If the function succeeds, the return value is nonzero.
If the function fails, the return value is 0 (zero). To get extended error information, call GetLastError. The function fails if the requested write operation crosses into an area of the process that is inaccessible.
Remarks

WriteProcessMemory copies the data from the specified buffer in the current process to the address range of the specified process. Any process that has a handle with PROCESS_VM_WRITE and PROCESS_VM_OPERATION access to the process to be written to can call the function. Typically but not always, the process with address space that is being written to is being debugged.
The entire area to be written to must be accessible, and if it is not accessible, the function fails.

it not happen or i do something wrong

Yes

if(*(int*)0x00910BC1 == 1)
{
//Is wrong? sorry idk int*
}

Is it the correct address, you've verified it?

yes correct adress , i tryed read and if value == 1
edit other memory address using simple memcpy


not problem with writing, i think read not working

Try out this tutorial. The process cannot be completely hidden, you should be able to find its PID. (Spy++)

I don't see how that snippit of code would work anyway, you're essentially just using a Hex value, not actually treating it as an address. When you use it on the function ReadProcessMemory that's when it uses it as a pointer and reads the value at that address.

Edit: If it's a popular game you could try searching for its PID or tuts on hacks for the game/open source. Read through and find what you need to make yours work and learn by example.
Edit2:Dereference Hex value that is a pointer to type int? Idk if that actually reads the memory though...