Yes, because names are proper nouns. So they must be capitalized.
No. Not unless the sentence begins with friends.
If referred generically as you did in your question, no. But, a specific one, such as Facebook, should be
Yes.
Yes, "PC" should be capitalized in a sentence.
No, the word forecast should not be capitalized in a sentence.
No, the word "fifteen" should not be capitalized in a date within a sentence unless it is the first word of the sentence.
No, "secondary students" should not be capitalized in the middle of a sentence unless it is a proper noun or at the beginning of a sentence.
Yes it should be capitalized.
Since "transition process" is made up of common nouns, it should generally not be capitalized in sentences. It should only be capitalized when it starts a sentence or appears in a proper name or title.
Have should be capitalized if it is the beginning of a sentence. Summer should not be capitalized.
Since 'felon' is a common noun, it is only capitalized if it is at the start of a sentence.
No, "methamphetamine" should not be capitalized unless it is at the beginning of a sentence.