Should be fine (although your ability to access work materials might be limited). Visiting the Shanghai office is a decent alternative to the tower's paid observation deck (similar situation at the Taipei 101 office)
Definitely did work. At least the Shanghai office before the pandemic.
Worked for me. Maybe someone filled a ticket to make it happen, I sure didn't have to do anything.
I've heard blockages in the Beijing Wudaokou office, but that was before I started working at Google (I left China in 2016 and started at google in 2020, so maybe a big gap). Maybe it changed? (or my info was wrong)