They didn't waste effort attacking parts of Oahu because by and large there was nothing to attack. Honolulu back then wasn't a very significant city and the rest of the island was largely empty (and by and large today it still is).

However, the US Navy Pacific fleet was a very significant target and that's where the impact was. Had they just come in and blown up Honolulu you may or may not have gotten the immediately US response that hitting Pearl did.

Even with the rudimentary technology of the day, the beginning of the attack was detected, it's just that nobody knew what to do with the intel. The fact that the Japanese were up to something was also known as we'd already busted their code machine.

No, you couldn't launch a sneak naval engagement today. Given the threat of nuclear attack from submarines, we've pretty much got tabs on even the underwater traffic, let alone surface shipping. In fact, surface shipping is trivial to track using the radar satellites. Even darkness and cloud cover won't obscure a big hunk of metal making a pronounced wake through the water in a SAR image. Even ATC radar would give a better warning than they had in 1941.