Is it normal to not know how to tie a knot(on anything), or ride a bike?

It's fine. I don't know how to ride a bike.

Sorry for putting two instead of to

I'm not good at physical tasks, they are harder for me to understand. So yeah its normal.

I like knots :D

I never showed an interest in riding bikes when I was young. It always baffled and annoyed me how some people at school would make fun of me for not knowing how to ride one, I just don't see what the big deal is with them.

I never learned to ride a bike for some reason as a child, and now I'm afraid to start learning because it'll possibly make me look silly.
I also can't swim, but there is a definite reason for that: MY parents wanted me to wear a swimsuit and nothing else to swim, and I wanted to wear shorts and a shirt over it. Not because I don't like how I look, but I don't like when people comment on it. As in I want to go swiming, not go listening to "OMG, ze's pale!" "How did you get this way?!" and a genuinely conerned "You know, your ribs should not stick out that much, you need to go eat something!".

I was a slow learner. I wanted to be able to:

(a) Tie my shoelaces
(b) Tie a necktie
(c) Tie a bowtie
(d) Ride a bike
(e) Whistle
(f) Blow a bubble gum bubble
(g) Tie a load of knots
(h) Make the wood pigeon sound with my hand
(i) Blow smoke rings
(j) Use a blade of grass as a reed for a hand instrument
(k) Do yoyo tricks
(l) Skate
(m) Do the really loud whistle with fingers in mouth

Of the thirteen, I still can't do three of them. :/