Understanding Society User Support

Hello,
I am studying the effects of a reform on rents paid by an household.
I need accurate information on when the household changed address.

How can I figure out if an household moved to a new dwelling?
I spotted two variables that can give me this information for renters: `w'_plnowy4 and `w'_mvyr (plnowy4 is recorded only from the second wave onwards).

What is the difference between these two variables?
My guess is that `w'_mvyr is recorded when an individual was first interviewed. Furthermore, `w'_mvyr is also recoreded for new joiners or
re- (joiners) that were interviewed for the first time at a certain address.

If an household moved to a different address, the information on when the tenancy started is recorded in `w'_plnowy4 (of course for all the
individuals that moved to that specific address at that time).

Do you think that what I wrote is correct? Could you please give me any other help?

Thanks,
Federico