I have few more questions, regarding my local registration issue and Blue Card

As one of my friend tried to help me to take an appointment with
Hanover ABH for Change of employer on my blue card, but Hanover ABH
has told to my friend that my visa or Blue card Residency permit is
invalidated. As per them if I stay out Germany for 6 months, It is
invalidated

my registration address issue:
Rental Agency gave me an apartment form date 01.11.2012 to 15.12.2013
at address 'X' and then my registration address was 'X’.

I had requested Rental agency to extend rental agreement upto
30.06.2014, but Rental agency gave another apartment from 01.01.2014
to 30.06.2014 at different address 'Y' and then
this address was not updated at local registration office .

This was my complete mistake as I was thinking to change address in
different city and then update to local Registration.

Because my changed address was not updated at local Registration  ,
that time local registration officer might have visited my old address
to enquire about me , but that time landlord was staying in the house
and he has told to Local registration officer  that he was not aware
about me.

Having above issue and I don’t know it till yesterday as I have called
Rental Agency to know it

Could you please advise me

Thank you a lot for your help


Regards
tbrao