There is absolutely no difference in Messenger Plus! between the "old" and "new", in context of the optional sponsor.
You had, and always will have, a choice to install the optional sponsor or not. And apparently you have choosen to install the optional adware sponsor when you updated. Which is rather odd because the choice is made extremely clear to you so you don't do this by accident (far more clearer then in the old setup)...
The optional sponsor is adware, not spyware, not a virus, but adware. If you have installed it, you could simply removed it by uninstalling Plus! by going to add/remove programs in Windows (where every other program is which you can uninstall).
You shouldn't have had to use any anti-virus scanner, anti-spyware scanner or what not (like Adaware) to remove the sponsor as that would have broken the proper uninstallment. The logic way would be to first look into add/remove programs to find an uninstaller of the program you want to remove...
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Thus, downloading the old one will absolutely make no difference and will not help you at all. Instead, download the current one and properly read the setup screens...