Hi.
To start, this TV should not require service remote to access service menu or adjustment menu.
In service menu also there is not a single reset option, but the technician must set the values one at the time.
About the part purchased, I could not find any JVC 87274RS remote control. Please check the number, include any dash or spaces, and include any info you have on the part, so that we can spread light on this.
About the problem it does not sound like something that "just need a reset" it looks like HDMI port is defective, and you should be entitled to get a technician at home if the unit is still in warranty (check it out).
Here how to get in service mode. You use the standard remote. Do not change values in service mode or you can damage the TV:
I uploaded here a service manual for the 40'' of same chassis.I do not have the 42''. Service mode, most parts and functions are the same. Panel size and frame are different.
Regards.
Ginko.