Use code search on your JVC URC to find something that handles some or all function of your Coldstone TV. If a search through all codes stored in the JVC URC fails, try a different one.
Universal remotes have severe limitations and aren't suitable to replace a lost or broken original remote.
If a genuine replacement cannot be found, try searching for a compatible remote. These provide most of the functions of the original including menu access. I think I bought mine from Amazon or ebay and it cost little more than a good universal.
Because you have rooted your TV or your TV comes rooted. Some app makers make their app not to run on rooted devices.
You can try unroot the TV or look for older or modified app version that runs fine with root.
It is also possible to hide root detection, but i do not recommend messing with the TV.
The mounting screws must be the correct metric size to avoid creating a safety hazard. Remind Currys that you have not received the hardware but also contact JVC to request the hardware. Before installing the TV, check to be sure the hardware is correct particularly with regard to length.