Documents required to change Tier 2 ICT to Tier 2 dependent from within UK

[Gowthaman02]

Hello

Iam on UK Tier 2 ICT visa valid till may 2020 and my wife just reached UK on Tier 2 ICT sponsored by her employer.Iam applying to change myself as her dependent.Iam bit confused with the documents.So please help me on the below queries.

Her sponsor had certified maintenance of the migrant ( and dependents if applicable) in the COS.Do i need to still provide my bank statements to prove maintenance as iam applying separately?

Documents showing you and your partner are living together.I dont have any documents (utility bills,council bills ,NHS letter) to prove this in UK as she reached only a day back.Iam planning to open a joint acc in both our names and get letter from the bank stating we are living in this address as per the bank records.Can i go ahead with this? If not,please suggest an alternate.

In the dependent application,they are asking for the below details .
What is the start date of your current visa or leave to remain? - Is this the issued on date in brp card or date of entry into the country?
What is the end date of your current visa or leave to remain? - hope this is the valid till date in brp card.

Do i need to provide any cover letter from her employer or immigrant lawyer?

Thanks in advance.

Thanks
Gowthaman J