LED lights, SWITCHES and between :)

1. I assume it asked to make it buffer because in VHDL (pre 2008 version) it is illegal to read outputs of a module internally. Making it a buffer makes it readable, but this can give you problems in larger designs where you istantiate many modules as buffers can only be connected to buffers.

2. Here, I use _i = internal and _r = register. Its a faily common convention

3. You simulate using modelsim. You will need to write a testbench to drive your code. There are plenty of tutorials on the internet.

4. Nope. That will just turn it on 4.9999995s later. Remember, with a 50Mhz clock, it takes 50000000 clocks to make 1s. 5s would be 250,000,000

Also, because GRID1/2 are set to 0 at the start of the process, they will only be lit in the states where they are explicitly turned on. If you want to turn a signal on and off at different points in time - remove the default assignments at the start of the process.