هَمْزَةُ الْوَصَلْ Hamza tul wasl

Look at these sentences:

1. هُوَ آبْنُ آلْمُدَرِّسِ huwab nul mudarrisi He is the teacher's son.
2. اِبْنُ خَالِد ibnul khalidin Khalid's son.
3. اِسْمُ الْطَّالِبِ مُحَمَّدٌ ismuT Taalibi muhammadun The student's name is Muhammad.

The alifs shown above are آ, اِ, ا. This types of alif:

1. are called  هَمْزَةُ الْوَصَلْ Hamza tul wasl.
2. appears at the beginning of a word.
3. are pronounced if it appears at the beginning of a sentence.
4. are not pronounced if preceeded by a another word or letter.

My comment
Based on what I've read in the Quran, I think only this alif آ is called Hamza tul wasl. The other alifs ا, اَ, اُ, اَ etc. are not called Hamza tul wasl. They are normal alifs with vowels. Thus, I am in doubt.