Why can't I play with two hands on the piano?
It is much harder to combine the elements of the two hands if you haven't fully understood the rhythm of what is playing on both hands. It is much better to have a clear idea of the rhythm. Practice just tapping your hands to the beat if you need to. Spend plenty of time practicing each hand separately.
Can you play piano with two fingers?
In most chords, only two fingers really matter. And the truth is: You can get rid of all the other tones in your chord, keeping only these two notes and your chord will still sound great. What are those tones?