At the beginning of this thread, it was stated that Bitcoin Core was able to handle both blockchains, and I quote: "The safest thing to do is to use Bitcoin Core as it is a full node and gives you control over which chain you want to use (via the invalidateblock and reconsiderblock RPC commands)."

I really thought that you would need 2 core nodes running now... one for the "original" blockchain and another for the "new" blockchain, but it makes sense the same program can run both just by an option on which one to use.

Can someone elaborate, or guide me to where I can find more information on how to select each blockchain? I thought that these commands were only to eliminate blockchain starting from the block indicated... but I can also see how that would make you to go form one fork to the other if you invalidating the block on the height of the fork. Still not sure I understand how that would "connect" you to the main blockchain, or to the alt blockchain.

After looking for 1 hour around for this, I think one of you might guide me since all explanations are not that clear.

Thanks in advance for the guidance!