Can a Prapanna chant the “Hare Rama Hare Krishna” mantra? Furthermore, can a Prapanna visit the Krishna Sannidhi at ISKCON and worship their Acharyas? Is there anything wrong with bowing with hands folded in front of their deity?

You can chant the Hare Rama Hare Krishna mantra. There is no harm in bowing with folded hands. However, we should not give up our sampradaya. Their sampradaya is different. Ours is the Sharanagati sampradaya, and we must not forget that.