Can Himawari Activate Tenseigan?

She technically already has the necessary DNA and chakra to manifest the eye. It was stated that you need a Hyuga Byakugan and Otsutsuki chakra to awaken the Tenseigan.

Can Himawari unlock the Tenseigan?

He cannot awaken the Tenseigan as well. So that only leaves one person with the chance to awaken the Tenseigan, and that is Himawari Uzumaki. Unlike Boruto, Himawari Uzumaki had awakened the Byakugan. She may not have the power to control it now, but she'll soon be able to do so.

Who can activate Tenseigan?

To awaken Tenseigan ,one need to have baykugan and Hamura otsusuki's chakra . Hogoroma otsusuki's chakra won't work . As sharingan / rinnegan was passed down to hogoroma aka sage of six paths and baykugan/tenseigan was passed down to hamura from their mother kaguya otsusuki.