who is the 'applicant' (AP1) when buying out my sibling

My sister and I have inherited my late mother's home. The property has been registered with the land registry so both our names are on the title. we have agreed that I will buy her share. We have each completed and ID1 which has been certified and the TR1. I have completed the SLDT1 and paid the HMRC customs and excise the Stamp duty due. I am now completing the AP1 to send to the Land Registry with the ID1 forms for each of us and the TR1. 

In the Panel 5  of the AP1  I have listed ID1 for myself  an ID1 for my sister and a TR1. Do  I need to send a copy of the SDLT1 and / or a copy of the Official copy of register of title ?

In Panel 6 of the AP1 who is the applicant ? is it me or both myself and my sister ?

Thank you in anticiaption of some clarity

 

Fiona - yes re HMRC SDLT confirmation/certificate. No re copy register as we hold that information 
The ‘applicant’ in panel 6 is the one going (staying) on the register, so you 

thank you Adam :)