'For for' bothers me in all of them, but I see no solution. I like #1 best.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
KJinCali79She was very curious for whose autobiography he had been looking for so many days.Ouch! That one gives me a headache, KJin. 'Curious for' is not possible, I think.
Mr. Tommost natural way'about' seems pretty natural to me, but there's nothing incorrect about the others. 'regarding' doesn't strike me as the best choice.