英文使用比較時，有關約簡詞 e.g. do have be(is, are)的問題

Q1. The original sentence is:
I have more model cars than my younger brother has (many model cars).
The main verb in this sentence is [have], but when we use [have] for the subject [brother], 3rd person, singular, then we have to use [has], since the form形式[has] is different from [have], so we write [has] in this clause of comparison.
Q2. the original sentence is:
A litre is more than a pint (is much).
The main verb in this sentence is [verb (to be) in (is) form], and in the clause of comparison the verb is also (is) form, so since it is the same form of [verb to be], we do not need to write it out again.
Q3. When the main verb in the sentence is [have] you need to use [have or has] in your clause of comparison. When the main verb in the sentence is [verb to be], in your clause of comparison you need to use [verb to be] in your clause of comparison. When the main verb in the sentence is [not (have) and (be)], you have to use [(do) or (did)], in the clause of comparison.
example of the 3rd kind:
John runs faster than I do.
John runs faster than Peter does.

Hope this helps!