just some add up.
1) Simulation is one way of verification and there are other ways to verify a design, such as LVS, formal verification, etc.
2) Corner case can have many meanings. In functional verification, corner case can be the test cases which is not covered by general test cases. In Synthesis, corner has a special meaning of different working environment. For the normally used three corners situation: fast corner (high supply voltage, low temperature), normal corner (normal supply voltage, 25 C), worst corner (low supply voltage, high temperature)
5) High impedance normally means large resistance which constrain current to a very low volume.
6) Timing info in cell libraries are use to calculate the delay of certain circuit. The constraints represent the delay we want the circuit to be. By change to structure of certain circuit without affect its function, we may get faster circuit which meet the constraints. This is what the optimization do in synthesis.
7) DFT, design-for-test. Normally means insert scan chains to RTL circuits. Insert clock gate to generate slow clock for scan chains which can be used when test the chip. BIST to test the function of memory components. And some time other test circuit for special circuits. These test function can be added in design, such as the clock gate, test control pins, or special test circuits. Scan chains are most likely to be inserted automatically by the synthesizer.