You make the best combination of your hole cards and the community cards. So if you have Ah Ad in your hole cards and the community cards are 10h 6d Ac Ks 2s, you’re hand is Ah Ad Ac Ks 10h.
An important note is that you do not have to use any of your hole cards. If the community cards are A K Q J 10 of Spades, then your hand is the same the community cards (along with everyone else). In this case you do not use your hole cards at all to make your hand.
This situation sounds like what restraining orders are designed to help with. IANAL, but restraining orders generally cover all types of communication, including social media. Showing that he has continued to harass you even after blocking him is good reason.
“You should stop posting these online, it’s really embarrassing because your [tool name] is such a failure. I should redesign all of it for you because I’m actually an engineer at [company name] and have a lot more experience. I could actually do it right, unlike you. I just might help you if you ask me nicely.”
Out if curiosity, have you ever tried calling his bluff? Reply with how would he improve it by saying any constructive criticism is appreciated. Something like
Do you have any recommendations on how to improve it. Looking to make as good as I can.
Depending on how you’re feeling, you could incorporate tagging their company. Use the same language they used. Something like
I’d love any constructive criticism from an actual engineer from @company
That said, it seems like the time to reply like that has past and it’s best to ignore/block him at this point.
Interviews work both ways. You are interviewing them just like they are interviewing you. They are doing you a huge favor in acting this way. Now you know you don’t want to work for them. This is much better than them pretending to be nice and you finding out later that it’s miserable.