It doesn’t matter for simple animation. you can convert from SWF version 7 file. But actually there are many restriction for LWF, like http://gree.github.io/lwf-demo/pdf/FLASHforLWFproductionguideline.pdf , because the goal of LWF is not for making yet-another-Flash-player-implementation, LWF just uses Flash for the convenience for authoring 2D animation (as you know, Adobe Flash is one of the best tool for creating 2D animation).
LWFS, the tool for conveting to LWF data from Flash data, helps you a lot. Please take a look at the document.