A public profile is a page where you can show your trading results to others. The numbers on it come from trades imported through your connected exchange keys, not from manual entry.
A profile is created switched off. To publish it, open the Public Profile section, enable it and save.
Yes. The public profile settings include a rolling visible period and an earliest visible date, so you can publish only recent trading and keep older history out of the public page.
Both settings only affect what visitors see. Your own journal keeps the full history.
You control visibility in groups rather than trade by trade. You can publish all trades, only closed ones, only open ones or none at all, choose which connected accounts are included, restrict the visible period, and hide notes, tags, categories, images and conclusions.
Leverage, balance and profit measured against your deposit are never shown publicly. To publish a single trade instead of a profile, open it and use the share link.