3 typing questiuons (questions for the smartest people here) ;-)?

[Bec]

1) It is because "I" is a pronoun used instead of your name (unless you refer to yourself in 3rd person). You capitalise pronouns (names)

2) definition of "vowel" in a dictionary and you'll have the basic answer. For example:

1. A speech sound. .. created by the relatively free passage of breath through the larynx and oral cavity, usually forming the most prominent and central sound of a syllable.
2. A letter, such as a, e, i, o, u, and sometimes y in the English alphabet, that represents a vowel.

"Vowel" refers, FIRST of all, to a type of SOUND --one in which there is minimal blockage of the airflow. With a "consonant", on the other hand, there is significant blockage (sometimes even stopping the airflow completely, as with "stops" -- b, p, t, d, k, g)

The usage of "vowel" for a LETTER is secondary, based on this first meaning. Things are simple for a,e,i,,o and u because they are ALWAYS used to indicate "vowel sounds".

Y at the BEGINNING of a syllable marks a consonant sound (and so may be called a consonant) examples: yak, yellow,

Y elsewhere in a syllable (middle or end) represents a vowel sound (and so is called a vowel). examples -- the many words with a -y ending/suffix: happy, funny...

Our letter Y is originally borrowed from the Greek letter "upsilon" -- which is a VOWEL

3) # (hash tag, hash key, "number" or in the Us apparently pound sign) - more recently you see it on social medias (twitter) as a "hash tag" - no idea why. I think it's like tagging on Facebook.
It is also used as a number sign - #1 means number 1.
In the US it is used rather than lb (weight) for pound (not the £ that we would immediatly think of).