This article points you to using load from file method: https://www.ptc.com/en/support/article/CS192244?source=search I think the steps would be the same for WTParts as with WTDocuments.
You used to be able to use "Insert" method to load a previous version but no longer. This is a critical part of system and data integrity to test test test.
The loading Guide (https://www.ptc.com/support/-/media/support/refdocs/Pro_INTRALINK_8,-d-,x/11,-d-,0/WCDataLoadGuide_169024.pdf?sc_lang=en&source=search), page 17 explains what you need to be concerned with:
More About wt.part.LoadPart.beginCreateWTPart The method wt.part.LoadPart.beginCreateWTPart supports versioning. This allows a part to be created at a specified version and iteration. Multiple part versions imply a sequence. For example, subsequent bulk load runs can fill in the gaps, but they do so by attaching to the latest iteration of the previous version. If a newer iteration is added to the previous version, the new version is attached to the new latest iteration. For example: Load set 1 (E.1, A.1, C.2) results in (A.1, C.2, E.1). The predecessors of: C.2 is A.1, E.1 is C.2. Load set 2 (B.1, A.2, C.1, C.3) results in (A.1, A.2, B.1, C.1, C.2, C.3, E.1). The predecessors of: B.1 is A.2, C.1 is B.1, E.1 is C.3. The iteration history of B.1 shows both A.2 and A.1 The iteration history of C.1 shows B.1, A.2 and A.1 The iteration history of E.1 shows C.3, C.2, C.1, B.1, A.2 and A.1 Any new versions or iterations that are added continue to change the predecessor links to the new latest iteration of the previous version.
