Taking a Mezuzah from a Rented Apartment

I rented an apartment, and there was a place where there was no mezuzah. I asked a rabbi, and he told me that a mezuzah must be put there. I told my landlord after I put up the mezuzah, and he told me that he had asked a rabbi at the outset, and that the rabbi told him that a mezuzah does not need to be put there.
Now I am leaving the apartment.
A. Am I allowed to take the mezuzah and leave it without a mezuzah, since my landlord’s rabbi told him that a mezuzah is not needed there?
B. If it is forbidden to take it, is it permissible to replace the mezuzah with a simpler mezuzah, and likewise one written in Beit Yosef script instead of Ari script?
Thank you very much.

Shalom u'vrachah. 

A. You may not take the mezuzah, as is the rule with anyone who leaves his home, and there is also danger involved in doing so. 

Even though according to the landlord’s view there is no need to put a mezuzah there at all, nevertheless the obligation of mezuzah is upon the tenant, not upon the owner of the apartment. 

B. You may replace the mezuzot with other, less expensive mezuzot, or with ones written according to a different custom, but only while you are still living in the apartment. You may not remove the mezuzot when you leave, even if you are putting up other mezuzot.  

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