F3 bio (red blood cell)

you ignored the most important fact.
are the red blood cells needed to move by themselves?
NO! they are just carried by the blood flow passively. they don't need to move or control metabolic activities, like contraction of muscle fibres.
(heart muscles do need, however; flow of red blood cells / blood is maintained by heart!)

the main function of RBC is "to contain haemoglobin"; few reactions / functions are undergone. RBC even do not contain nuclei, suggesting that there's little need of control of metabolism -- process requiring energy.

Red blood cells do not move by themself,
they all move by the pressure provided by heartbeat.
And it is the reason why red blood has a low density of mitochondria.

it's because the red blood cell do not need much energy.

for question2,the red blood cell carry the oxygen by some chemical change,not need energy input.
In fact,the oxygen combine with red blood cell,and to transfer the oxygen as the form of oxyhaemoglobin,which would occur when the concentraction of oxygen is high,and when the concentration of oxygen is low,it would change to oxygen and haemoglobin.