It is proper grammar.
yes
no had done or has completed
If you are writing proper grammar you should not use 'then' at the beginning of a sentence.
proper
"She did not have" is the proper grammar.
It is proper grammar.
yes
"Don't it" is not proper grammar. The correct form is "doesn't it".
It is proper grammar to say, "I bet you".
no, that is definitely not proper grammar.
no had done or has completed
In America we use the older form have gotten rather than have got when using it as a past participle, as in "I have gotten over it." But in constructions such as "I've got a secret," both sides of the pond are in agreement.
If you are writing proper grammar you should not use 'then' at the beginning of a sentence.
proper
No. Had gotten would be correct.
What was there is proper grammar.