Why should we buffer reset line?

1. It's actually used as a level-shifter. It's converting the 3V PCH_PLTRST# to a 1V open-drain signal. In many cases, the reset input of a CPU can also act as an open-drain output, so the CPU can reset the surrounding system. If that's the case, you shouldn't drive the reset pin using a push-pull signal, otherwise it will create a short circuit when the buffer drives high and the processor pulls low.
2. -
3. R32 is the pull-up, see above. Not sure about the purpose of R34 though.
4. The special resistor symbol stands for a bridge made by solder or directly on copper on the PCB, but still offers the possibility to remove the bridge and install a component. The @ near means, that no component is installed.

The 74LVC1G07 is open-drain, so it looks like it is used as a voltage translator from 3V to a lower voltage (1.05V). R32 is the pull-up.

R34 is used to minimize reflections and will be found close to the buffer end of the trace.

R35 appears to be an optional strap low and I would expect it will be unpopulated.