Program the output frequency for any repeater (not just amateur radio) in order to hear all of the traffic on the repeater.
The input frequency is what the mobile/portable/base station users transmit on to talk through the repeater, meanwhile, all other users listen on the output. That's how that works. So unless you want to try to listen to someone talking through a repeater real close to your location, monitoring the input is pretty useless.
DSTAR is ICOM's version of digital voice/data transmission for the Amateur Radio community, there currently are no scanners that can monitor it, you have to use a DSTAR radio by ICOM or KENWOOD in order to receive transmissions.
YSF (Yaesu System Fusion) is a mixture of FM, and or C4FM Digital Voice/Data transmission which is designed by Yaesu for the Amateur Radio community. It too cannot be received by scanners. You have to use a Yaesu (system fusion) radio in order to receive voice/data transmissions when they are in digital. The whole System Fusion means that the radio system is capable of automatically detecting if a signal received is FM or C4FM Digital. So if Station A is talking through a YSF repeater with an FM radio, it will repeat in FM to everyone, but if Station B keys up in C4FM Digital the repeater will automatically restransmit the signal in C4FM Digital and everyone with a YSF radio will automatically hear Station B's digital transmission.
Hope this helps a little bit.