FAQ for
"Detective Conan" (1996) More at IMDbPro »"Meitantei Conan" (original title)

Yes.It was discovered that when he has a cold,a drink of a certain type of liquor will restore his body to normal.This happened in episode 49.The second time,in episode 191,Ai made a 24-hour antidote pill for him.The third time was in movie 7.The fourth time was in episode 521.The fifth time was in OVA 9 (though he was unconcious the entire time).All five times though,he has reverted back to Conan.

Yes,three times.The first time was by Conan in episode 54.And it was an accident,as he was aiming for Kogoro.Yet because the dart only hit the cloak tag in Ran's pocket,it didn't knock her out.The second time was by Shinichi in movie 7.And the third time was by Ai in episode 523.She was tranquilized both of these times because she was about to see Shinichi turn back into Conan.