what is the name and the rules for "sentence + , question?" this grammar?

[yyen]

for example,
1.
the name of this grammar: Tense: past tense
i ate an apple.
'ate' is the usage of past tense

2.
the name of this grammar: conditional sentence/ conditional clause/ if clause
If i don't finish the homework before 7:30p.m., i will not allow to watch TV.

3.
the name of this grammar: Complex sentence: Relative Clause
Watt was an engineer.
He invented a steam engine.
→Watt was an engineer who invented a steam engine.

4.the name of this grammar: Subjective-Verb Agreement
My friend was late for the class.
My friends were late for the class.



And if,

A.Peter had bought a toy, didn't he?
B.Peter had bought a toy, hadn't he?

What is the name of this grammar?


relevances:
w ww.usingenglish.com/forum/ask-teacher/179205-what-right-sentence-should.html#post930197
w ww.usingenglish.com/forum/ask-teacher/179206-what-rules-grammar.html#post930198

HELP ME!
Thanks in advance.

[emsr2d2]

Welcome to the forum.

Please ask different questions in separate threads and please don't use so many different colours. Some of them are very difficult to see on the screen.

[yyen]

ok, i have changed, and separate the questions in different threads.

[emsr2d2]

OK, I have changed it, and separated the questions into different threads.

Thank you. Please remember to capitalise "I" at all times, start every sentence with a capital letter, and that "OK" is always written in capital letters.