Interesting Stuff

I’m playing in a club game with a regular partner. In fourth seat, I pick up:
♠ Q873
♥ 42
♦ A54
♣ A1097

Dealer passes, partner opens 1C, and RHO overcalls 1S. I bid 1N, showing a weak, balanced hand with a spade stopper and no interest in hearts. Partner raises to 2N, and I’m at the top of my range and happy to accept the invitation to 3N, which everyone passes. LHO leads the queen of diamonds, and I get to see dummy:
♠ KJ102
♥ K97
♦ 963
♣ KQ2

About 6 HCP lighter than I expected! I later asked my partner why he bid 2N instead of just passing 1N with a balanced minimum opener like this, and he said he wasn’t thinking, and this was a mistake. Okay, we’re in the wrong contract, but let’s see what I can figure out. →

I’m playing in a Just Declare tournament on Bridge Base Online, which means the hand has been bid by 4 robots, and I’m taking over the South seat after the auction has finished. The bidding is complicated: