How does internal mobility internationally work in a BB?

I am a 2nd year research analyst at a BB in NYC, and I'm interested to transfer to London. My significant other lives there, so I'd like to be reunited with them in order to increase my work-life satisfaction. Wouldn't mind doing the same type of work as I do now but at the London office.

About a year and a half into my current role; I prefer to transfer after reaching the two year mark in NYC, if possible. 

Have a few questions:

• Is it acceptable to seek out multiple roles while waiting for an open slot on a particular team?
• At what point do these discussions with HR not become confidential to my existing team and manager if I transfer but do different type of work?
• If I want to do the same work in London, at what point should I disclose my interest to transfer to my existing team and manager and ask for help?
• How long does the process usually take?
• Is the interview process any different compared to interviewing as a person who does not work in the firm?
• What are common hurdles in the process and how do I manage them?