@Jimmy329
I’m not sure about what you meant by “short ng”. Is “ng” the short one and “nang” the long one? If so, then the confusion might happen only when they are spoken because they sound the same. However, when written they are unrelated.
The following is about your Nos. 2 and 3 in the list:
“Ng” is a preposition that translates to “of” most of the time. It may also serve as the indicator of the object of a verb.
Laru
án NG b
ata = toy OF a child
Alas s
ingko NG um
aga = 5 o’clock IN the morning
Unang araw NG buw
án = first day OF the month
Umin
óm siya NG kap
é = He/She drank coffee. (drank what? = object)
“Nang” is the adverb “when”; is used to form an adverb; is used as a conjunction; is used when an action is repeated.
Gab
í na NANG umal
ís sil
á = It was already evening WHEN they left.
Lumal
akad siy
á NANG mab
agal = He/She is walking slowLY.
Umin
óm ka ng kap
é NANG (or “para”) hind
í ka antuk
ín. = Drink coffee SO THAT you won’t feel sleepy.
Iy
ák NANG iy
ák ang bata. = The child KEEPS ON crying.
B
akit t
ulog ka lang NANG t
ulog kahit mar
aming mga b
agay ka pang kail
angang gaw
ín? = Why do you just KEEP ON sleeping even when there are a lot of things that you still need to do?
With regard to the meanings you listed, what you are describing in No. 1 is the linker “na” and not the preposition “ng”.
No. 1: < “Na” can serve as a linker between adjectives and nouns (in general: modifier and modified word).> In almost all cases, the modifier and the modified word are interchangeable as long as “na” remains between them.
it
ím NA sap
atos = sapatos NA itim = black shoes
pap
él NA pun
ít = punit NA papel = torn paper
When the word before “na” ends in a consonant, except the letter “n”, the “na” stays between the words as is. (The example above illustrates that).
When the word before “na” ends in “n”, the “na” may be attached as the letter “g” to the end of that word.
ibon NA lunt
ian = ibonG luntian = green bird
luntian NA ibon = lunt
ianG ibon = green bird
h
ipon NA malak
í = hiponG malaki = big shrimp
malaki NA hipon = malak
íNG hipon = big shrimp
When the word before “na” ends in a vowel, the “na” may be attached as the letter “ng” to the end of that word.
kab
ayo NA put
î = kab
ayoNG put
î = white horse
puti NA kabayo = put
íNG kabayo = white horse
pay
át NA b
atà = skinny child
bata NA payat = b
ataNG payat = skinny child
2. and 3. were covered above.
4. <"ng" can be a linker between a personal pronoun and an infinitive verb (e.g. gusto kong kumain ng pancit) - this is contracted. But as far as I understand, sometimes the "ng" is simply omitted !> - No. It’s not “ng”, it’s “na” that you’re describing here. Please look at my post under the post of jeffkrauss regarding sneezing. I explained the case of having 2 verbs in a sentence. Your “gusto kong kumain” is another example of having 2 verbs – like and eat. The linker is “na”.)
5 <"ng" can be a linker between a personal pronoun and a noun (gusto ko ng aso) - so it is not contracted.> - “Ng” is indicating the object (aso/dog) of the verb (gusto/like)
<How about the general rules for contraction ? "ng" is contracted, when it is a linker, unless it is a linker between a personal pronoun and a noun ?> - Given the explanations I have given above, do you still think it’s a matter of contracting “ng”?
<I am always in doubt, when I have to use "ko ng" or "kong", "mo ng" or "mong" etc.> - “Ko ng” and “mo ng” are personal pronouns followed by the preposition “ng”.
“Kong” and “mong” are “ko na” and “mo na” ("na" is the linker "that/which/who is") merged based on the explanation I gave under your No. 1, i.e., when the preceding word ends in a vowel, the linker “na” may be attached to the previous word as “ng”.
BTW, I said that the " 'na' may be attached ” because although we customarily do so, it is not wrong to leave it unattached.