about force and motion

1 ,
NO
first of all , you have to understand that
action is body A on body B
reaction is body B on body A

for your case
weight is our body (body A) attracted by the Earth (body B)
reaction force is the floor on (body C) on our body (body A)
(if you are sitting on a chair , chair will be body C)

2 , Yes
but just to remind yourself , only 2 body is involved
for example , when we are in a lift going up from 1/F to 9/F
just when the lift accelrate upward , you feel yourself "heavier"
but your weight do not change at all

this feeling is just because the floor apply a larger force on you
so that you can accelrate upward with the lift
this can be consider as a action force ( floor on you)
at the same time , you are also applying a larger force on the floor (you on floor)
(this can be proved by standing on a weighting machine)
this is the reaction force

vice versa , when you travel from 9/F to ground level
the lift accelerate downward , you feel yourself lighter
at the same time , you will find the reading on the weighting machine drop

1. Weight and Normal reaction is definitely NOT an action-reaction pair.

Two forces are considered as action-reaction pair when
~The two forces are acting on different bodies
~They are equal in magnitude, but different in directions
In this case, although weight and normal reaction satisfies the second statement, but the first statement is not fulfilled since both weight and normal reaction are acting on the body.

[Supplementary Information]
The reaction pair of the weight is actually the gravitational force by the body on Earth.
Gravitational force actually refers to the mutual attractional force between two bodies. The mutual attractional force are then considered as action-reaction pair since they satisfies both the two statements.

2. Newton's third law of motion DOES apply to motion involving vertical acceleration.

It should be highly mentioned that a motion in a 3D space can actually be considered and studied separately into three mutually independent dimentions. In this case, not matter what kind of motion is on the vertical direction, Newton's third law of motion can be applied in the horizontal direction / other mutually independent directions.

Hope the above information can help you =)