Hi,
I have a simple connection between points A and B. Lets say it has some delay 'd' due to wire resistance.
Now, can we put a buffer between A and B such that the delay can be reduced.
Yes you can in my opinion. This is referred to as registering a signal. The timing only needs to be considered before and after the buffer individually. The propagation delay will be lower as the buffer "splits the timing path".
The propagation delay portion however is typically lower than the logic delay so doing this may not make as much of a difference as you would think.
Depends on length, capacitive load, operation frequency and the capacitance that is driven by the block before buffer. Most of the time if you require this type of improvement in normal circuit, it means that it cannot be automated so try other solutions. But in special designs like ALU's it is used to optimize every delay. In any case best way to cope with delays in metal lines is to get them closer.