the biggest your arms will get will be from chin ups pausing each rep at top for a few seconds and holding the negative on the last rep of each set as long as you can and I mean fight it all the way until you have to lock out.

Tris honestly cables produce more tri size for me now than dips or NGB. Leaning over cable over heads with a Vbar, jm presses with cable also with a v bar and skulls on trx straps body weight. All these with holding the last rep for 30-60 seconds on each set will add more size than dips or NGB if you’ve always done them.  Tris and bis seem to get a better workout with constant tension for me anyways.

I would say dips and do them the same way I said to do chin ups.

When in the history of the internet has this type of challenge materialised? I'm sure there have been a few occasions but mostly not.

You'd just need 2 guys willing to meet up, like in a week, and duke it out, no fucking waiting and stipulations and rules and all
that shit. Book an arena and sign waivers lol, none of that shit will ever happen in this case.