Is that chance's of time value will get same?

As OriginalGriff has pointed out, the chances of calling the time_t within a single second are quite high. For a point of reference, consider the following program

#include <iostream>
#include <chrono>

using Clock = std::chrono::steady_clock;
using Seconds = std::chrono::seconds;

int main()
{
    const size_t nsec = 2;
    size_t ncalls;
    auto start = Clock::now();
    auto elapsed = [start]() { 
        return std::chrono::duration_cast<Seconds>(Clock::now() - start).count(); };

    for(ncalls = 0; elapsed() < nsec; ++ncalls)
        time(0);

    std::cout << "performed  " << ncalls/nsec << " calls per second\n";
}

Running this on my desktop PC, I get over 23,000,000 calls per second. Even a pi-zero will generate about 375,000 calls per second. This is doing far more than just a single call to time() per loop, so the actual number of system calls is at least 2 times the value printed, perhaps even 3 or 4 times.

So its probably not a good idea to use time() to generate a unique number. You could use the time() call as a seed to the standard C random number generator (srand()/rand()). Or you could look into Pseudo-random number generation - cppreference.com[^]

You can use the Boost Uuid Library - 1.77.0[^] The documentation contains sample code, so it's not hard to use.

P.S.: if you don't want to use boost, you can find alternate suggestions with working code here:
How can I generate UUID in c++, without using boost library? - Stack Overflow[^]
The first answer just requires an up-to-date C++ compiler, the second should work in C if you remove the iostream output from the example code, but it will only work on Windows.

A compatible C ++ solution like that from k5054 is a good idea. Alternatively, you could use a multimedia timer.
Acquiring high-resolution time stamps - Win32 apps | Microsoft Docs[^]

Note: The time functions from the C library have a significantly higher resolution under Linux.
But this is about Windows, and the resolution of the C standard library is not enough for many things.

Quote:

Need to know about the time c-inbuilt function

Obviously you didn't even take the pain to read the documentation, because the documentation tells you what is time() and how it works, so you can deduce tyhe answers to your questions.
time - C++ Reference[^]