As Coolcryptovator said, the OP is completely unclear and it would be difficult for us to give a solution for your question.
Let me try to help you as far as I have understood the question
Where can I download
Download the latest version of bitcoin core from
https://bitcoin.org/en/download Once you have done so, run the client and the whole blockchain will be downloaded. The first block to be downloaded is the genesis block.
is it possible to make it identical with the original Genesis block?
Genesis block is the initial and the very first block of any blockchain. If you are trying to make an altcoin based on bitcoin, try to fork the project on github and change the code. You need to note that, the Bitcoin code is very complex and has changed a lot right from the 2009. So it isn't advisable for you to create a coin based on the current code. The code for changing the number of coins will be present in validation.cpp if you really need them.
The topic and code has changed a lot as it was in the topic. main.cpp has split up into 2 parts, segwit and other softforks has been put forth. It would be better to follow the topic and build an older version of core.
No you cannot, then you would be able to get all the private keys from the GENESIS block.
This is false. Private keys are not related to generating a new block. Private keys are used to spend the coins and they won't be exposed when a miner mines a block or when a programmer generates a new genesis block.
