Hi
I have interest in creating websites like imdb, popclogs.com, neopets or goodreads.com. I have some interest in writing a blog (so might need to change wordpress code), and I would also like to make phone apps that will also work on tablets, or on computer games like the Sims.
What should I be studying? I feel like I need to know a bit of everything?
Thank you
Game development is a very different branch of programming then making websites. I am not sure its wise to want both.
for websites you need html, css and Javascript for starters. Very likely a back-end needs to be added to your website, for this many language are available (ruby, python, javascript, go, java and more). As well as a database.
for games i would use an existing game engines like unreal engine 4 (or are they already at 5? ), which means you need to learn c++. Or you could look into unreal engine alternatives (just google unreal engines alternatives)
What kind of coding do I need to know to develop apps? maybe to create productivity, religious, mental health or gaming apps?
Thank you for your detailed reply, above
I’m getting the sense I’m in over my head (lol)
good, then that point came across 
there isn’t a universal answer to your question, if you make a simple app a tool like phonegap or react native (which is cross platform) might be good enough, while a heavier app would require native languages of platforms (java or kotlin for android, swift for ios and c# for windows phone)
or you might consider a web app is better for your application, with reactJS, vueJS or angularJS.
It sounds like Javascript would be a good thing to use, as it is for a few diffferent things
Its possible. But don’t forget that its impossible for me too mention everything, there is also kivy for python, which is also cross platform i believe. There simple too much.
Javascript does have its quirks, some people argue its a dreadful language.