This is a 2014 iMac model, whether the RAM can be replaced by the user or by Apple or by an Aurhorised Apple repair center, itself, is irrelavent.
If the OP still has the one free year of AppleCare or has purchased the extended 2 years of AppleCare, any breaking into the iMac's case WILL void such warranties, plus, Apple, itself, will refuse to do anymore service to the OP's IMac and, I believe, this applies to any future service if the iMac is ever broke into by the user as any iMac model has NO USER SERVICEABLE parts inside.
You are, potentially, telling the OP to void their Apple warranty.
Do what you want to your own IMac. That is your decision.
Don't advise others to do the same and, potentially, have their iMac refused for any type future servicing.