1. Stage 2 doesnt mean a lot. The GRS intercooler is a very good idea, and keeps the temperature of the air entering the engine nice and cool, for more power. Stage 2 probably means it's had a chip, boost increase and the intercooler.

2. Again, see above.
3. A turbo timer allows u to lock the doors while the engine is still running. You should not allow a turbo engine which has just been on boost to swicth off, as the oil in the turb is very hot and can damage things. Keeping the engine running allows oil to run through it for a couple of mins to cool it all down.