GENIE 3850R works very well with my GENIE receiver #315390R2 that I have operating an old Chamberlin opener.
The receiver was not included in the installation instructions but they were the same as the first (A) instructions you sent.
You probably know all this but just in case not I thought I would comment anyway.
Thanks
The liftmaster repair kit was exactly what I needed. The parts arrived very quickly and the repair went well. I had enough in the kit that I could rebuild my old part so now I have a spare if ever needed. Thanks for the great service.
Product shipping time and product cost were fantastic and fast! Fasteners included with product were not the usual garage door hardware and required different tools.