No, only the following line in the plugin must be adjusted for the new 3.6 plugins:
The new line should be:
in order to have the plugins working in VB3.6, the actual 3.5.x plugins will not work.

The 3.5 ones should work on 3.6 just fine without the executionorder line. I wouldn't think you would HAVE to have that line to make the plug-in work.

Shouldn't.

You can import 3.5 plugins into 3.6 fine - they get allocated a default execution order of 5.

You cannot import them the other way as a database error is generated. If you manually add the executionorder column to your 3.5 database (plugin table) then you can import 3.6 plugins into 3.5 and they will work fine (as long as the hooks exist of course, many new ones were added to 3.6).

I've come across quite a few 3.5 releases that don't work in 3.6 due to either clashes with new 3.6 functions or simply don't work. Although saying that about 60% or the ones I did try have worked fine.

This isn't anything to do with execution orders though, it's just plain and simply that the code has changed.

maybe you shouldn't have to but..... unfortunately not a single one of my hacks worked on my 3.6 test forum. I had to remove them all, one by one, to get my forum to work.

All of my products are working, although I did need to remove a few that made it to the core code.