Yes, as in 'He was the lesser known author of the group'. Lesser can describe an adjective as in that sentence, or it can be used as a comparative, as in 'the lesser of two evils'.
"She did not have" is the proper grammar.
It is proper grammar to say, "I bet you".
"Don't it" is not proper grammar. The correct form is "doesn't it".
No! It is should HAVE plus the participle, often contracted to should've in speech.
no, that is definitely not proper grammar.
No, it is not proper grammar. The correct phrasing is "you and I."
What was there is proper grammar.
It is proper grammar.
There are many grammar practice websites that will help people learn proper English grammar. These are necessary since many people have no idea what proper grammar is these days.
yes
No
It's you are, you is is not proper grammar.