After discussion with deepak sir:
First of all point 3 is wrongly framed.
This are the points from Go classes telegram channel:
“There exists a Bijection between Set of type 3 grammars and set of all regular expressions... YES.
because both are countable infinite so have same cardinality as set of positive integers.
There exists a Bijection between Set of Turing machines and set of all regular expressions...?
Same reason. “
What is countably infinite?
→ when the set S has one to one correspondance with the natural number.
So,similarly “Set of ALL Grammars and set of regular languages both are countable infinite.”
Since set of all grammars has one to one correspondance with natural number and regular language has one to one correspondane with natural number.So this implies that surely there will be a bijection.