It depends greatly on the system. Most laptops you cannot, but there are some that allow you to. The best way is to try opening the system cover and see if you can locate the CPU. Usually they're in an easy to reach location if you can replace it yourself. If not, then you'll know.
There IS a way for you to tell users to "back off" privately, it's called "leave reputation". Same can be said when someone leaves you a helpful post (you can post positive or negative feedback)
Do you have the exact model name of the system, or can you install a program like Speccy (Speccy - System Information - Free Download
) and then post the output file? I can interpret it (or you can) and get a better idea of what the system is capable of.