I'll tackle the first two, and let a person more in sync with the pics do
the others.

> 1) What does open collector output mean. What should i consider in the
> circuit diagram for this pin.

This means that the output cannot by itself create a logic high. It can pull
current to ground, but it cannot output current to a load.  The output
circuit would look like an NPN transistor's collector, with the emitter tied
to ground.

> 2) What does weak pull-ups mean.

The chip has pullup resistors, which you might use with switches, such that
in the absense of any completed circuit to ground, the input reaches a high
state.  The pullups are "weak", in that they won't source much current.
Exact figures probably vary from chip to chip.

A strong pullup would be a 1 ohm resistor to VCC, a "weak" pullup might be
more like 100k.