When I come back home I will make a good impression between students about the college which I pursued my master's degree from.
The sentence is incorrect, e.g. "impression between students".
impression: a strong, favourable, or remarkable effect: he made an impression on the managers.
an effect produced in the mind by a stimulus; sensation: he gave the impression of wanting to help.
So I would say
When I come back home I will make a good impression on students of/about the college in which I am currently pursuing/taking my Master's degree.
(in case you are pursuing it now, and not in the future)
You don't need a comma, except possible after "back home". Commas represent pauses in conversation, so in order to make the text more eligible, you add commas.
For the second question the answer I would say is
When I come back home I will make a good impression on students of the college in which I will have completed Master degree.