Need to verify my developers claims, please help.

Hi all,
My business is currently on nopCommerce, and we like it very much.  However, we've run into a few problems since the developer here has hacked the core up, making features unreliable and upgrades long and error prone.  We've asked him to move his custom code into plugins, which he has begun, but now he is saying it is finished, when it clearly is not.  He also rebased his code on 2.6, but reports show that there are 400 file differences between his code and 2.5, and over 600 between his code and the latest 2.6.  We are also concerned that he is rebuilding the site on an unfinished, unreleased version of NOP.

His exact words were:
"nop 2.6 is the latest stable source control build version number; they change their version numbers prior to release..."

and when questioned why the core code doesn't match the official release, he said:
"I addressed this by creating a new project / solution outside of nopCommerce' scope that later gets built and added to nop's built code." - basically meaning he created a tag of NOP with his custom hacks and called it an 'new solution'

If anybody could please his explainations as plausible, we'd be very grateful.
Thanks
J

The latest stable and officially released version of nopCommerce is 2.50. Version 2.60 is still under development. See Download page

AFAIK It is impossible to change all parts of Nop just using plugins.

@ a.m.  thanks very much for your response.  It was very helpful.
@daveb I appreciate the response.  The problem hasn't been changing every part of NOP (we do like the core features), it has been that the custom changes to the code were reaching a point on being unmaintainable, and addressing that has been difficult since the developer's input has turned out to be less than accurate...