Am I required to upgrade? (Also extra question)

Hey there, I used to be really into modding with Mcreator, but I got out of it, so I deleted the application. I decided that I wanted to retry this, come back, and try to make a mod once more. The only problem with this is that most of my favorite mods are on 1.7.10, so I want to stay consistent and stay on 1.7.10. I downloaded the 1.7.10 Mcreator, and it tells me "You are using an outdated version, redirecting you to the download page..." each time I load it up, which is fine and all, because it still lets me in. It then asks me to log in, but won't allow me to for whatever reason. I just press skip at that point. I worked on my mod for a while, and then went to test it, but the test environment wouldn't load, and I have 0 clue as to why. Am I forced to upgrade in order to do anything, or am I missing something, like maybe I need the 32 bit version instead of 64 bit?

Also, side question, I made a mod called Johnny's Utopia a while back and would love to use it on my multiplayer server with friends, but it won't work on my Forge server for some reason, and I would love to know why. Thanks again!