Question about input delay

The device datasheet will have "d elay chain" section that shows the range of values you can put in and how much the delay varies, so you can control this.

1) Note that they are not PVT calibrated, so for example, if you were able to crank up to a 1ns delay at the slow corner, it might be a 500ps delay at the fast corner.

2) If you have I/O timing constraints, the fitter will try to modify the delay chains to meet your requirements. This is the recommended way to do this. (It's also why your timing may change as you dial in constraints. For example, I've seen people only look at the slow timing model and get some "slack" on their I/O. They then modify the their I/O requirement to a value that should make the slack what they want, but after compiling, the slack isn't what they expected because the fitter chose a different delay setting. This is usually because the fitter is aware of multiple timing models and trying to meet all, but can be annoying.)