Do I need 2 ID1's

My sister and I have inherited two properties from our late mother. We are joint executors. One property is going to my sister who wishes to sell and the other is going to me and I intend to live there.
Neither property is registered. Probate has been completed.
My question is will my sister and I need to fill out two ID1's, one for each property? 
As I read it I will need to supply her with an ID1 from me as well as signing her AS1 and she will have to do the same for me?

Would it be prudent of me to send a FR1 form in as well as an ID1 and AS1 form or does the FR1 come later after the property has assented to me.

thanks in advance

David - you will both need your identities verified. If there are two separate applications, one for each property, then you can link the two when lodging and rely on the one set of ID1s to cover both applications/transactions. Just make it clear on submission that is the case to ensure that the paperwork is kept together/cross-referenced as appropriate
You don't have to register the property being sold but a buyer may ask you to first before they will complete