What is the standard outer length of a loading platform on high levels of building structure and how it can be strengthened if there is no roof?

The best thing to do would be to engage a Professional Engineer who is competent, experienced and qualified to provide answer. This appears to be a Temporary Construction to facilitate the actual installations. All temporary construction that facilitates actual construction., eg., loading platforms, formwork, scaffolding etc should be designed by a competent person and checked by an authorized examiner at site. The role of construction safety professionals and project manager should be to ensure the right process is followed.