>1. When reincarnation is a reality, why many religions, exccept Hinduism, do not believe in it?
Because everyone is one a different level of spiritual understanding.Karma is God's cosmic teacher which makes sure all lost souls eventually return to him,it teaches by experience.
>Are there any indications (subtle or obvious) in ourselves to feel that we had visited this world before?
Our habits,personality etc,we acquired all this during our previous lifetime(s).
God bless.
joy