Both uplinkfast and backbonefast are features for classic spanning tree, not for rstp.
1, uplink fast should be applied on the switch, not on the interface
2, uplink fast will bring blocked port into forwarding immediately when it meets 2 conditions :
a) root port has lost connection from peer side
b) there is a blocked port in the switch that just lost root port
3, without uplink fast, when switch lost root port, the blocked port will have to go through listening (15 secs) and learning (15 secs) period before going to forwarding state; with uplink fast enabled, switch will save 30 secs to move blocked port into forwarding state.
1, backbone fast is used to speed up recovering for INDIRECTED LINK FAILURE. Indirected link failure means that switch has received TCN from peer switch A because switch A has lost root port (link towards root bridge failed).
2, Assume that port A on switch has received inferior BPDUs from peer switch A, it will ignore this BPDU because it is inferior BPDUs, instead it will continue waiting for root bridge BPDUs from peer switch A until max-age (20 secs by default) timed out. After that port A can go to listening and learning period.
3, With backbone fast enabled, As soon as switch receives an inferior BPDU it will send a root link query on its root port and non-designated ports to check if the root bridge is still available. Thus it will save 20 secs for recovery
4, Backbone fast is a global command, can not be configured in interface level.