I’m basing my response on my definition of “altering” and “reality”. Questioning the meaning of those two terms is not pedantic. It’s an imperative.
Is CERN affecting the future? Of course they are, as are you and I and everyone else on the planet. The future evolves based on everyones’ actions in the present and the past.
Have they altered the laws of physics? Are we still here, does the earth and the rest of the universe still exist?
If the laws of physics were to be altered even to the tiniest degree our universe fails instantly (at least locally. The effect will spread.). For example, ever so slightly change the electric charge on charged particles and the entire structure of atomic nuclei disintegrates - carbohydrates no longer exist, proteins no longer exist; chemistry as a whole fails instantly. Quantum tunneling of protons in stellar cores is based on the strength of the electric charge on protons versus the strong nuclear force. Alter the electric charge on protons and stars either blink out because the proton charge is too strong such that it overcomes the strong force that binds atomic nuclei thus fusion stops or the charge is too weak and all the protons come crashing down on each other because they no longer resist the strong force. The stars instantly fuse all 10^58 protons (class G stars, like Sol) and all those stars become, not super novas, but super-duper BMF KaBoom! thermonuclear galaxy-killing bombs when they instantly release all the energy that was supposed to last several billion years.
We are still here, the universe still exists so, no, CERN has not changed the laws of physics.
Has CERN created new realities? Have they expanded the knowledge base of humanity? If the answer is yes then they have created a new reality (reality as I would define it) where we know more about the world today than we knew yesterday.
What’s the bottom line here? Could CERN actually create a mini black hole? Frankly, no. But for the sake of argument let’s say, yes. What would happen if a dozen protons fused and formed a mini black hole? Not much. It would evaporate into photons in a few nanoseconds. You’d probably get a couple dozen gamma ray photons, anti neutrinos equal to the number of protons. That’s about it. The world won’t end or be swallowed up by a black hole. The core of our class G star has an average temperature of about 15 million degrees. Once in a blue moon a proton here or there will have a huge velocity (temperature) and might do some weird things. That’s normal. At the core of an atomic (fission) bomb before it expands beyond the tamper the temperature goes to about 10 billion degrees. Lots of really weird things happen. But the world isn’t swallowed up by a black hole and the laws of physics don’t change.
The laws of physics are ultimately quantum mechanical in nature and based on the relative strength of the strong, electromagnetic, weak and gravitational forces. Any change in the strength at all and the universe ends - probably instantly considering how distant particles are entangled. With any luck we might have a photonic universe with no matter.
I recall that Titor/TTO went on and on about how CERN was about to discover the secret of time travel within the following 18 months using the LHC. They didn’t. In fact the LHC had a serious quench event that took the collider off line for almost a decade. Funny, that. The time traveler from the very near future wasn’t aware of an event central to his saga that took place during his own lifetime.
I’m not concerned about CERN (pun intended).