A Couple beginner problems;

Okay, first of all, I have a Mid-2012 Apple MacBook Pro A1278 (I just upgraded from the stock 4GB of RAM to 16GB of RAM). I'm from a family of musicians... my dad bought Logic Pro X from the App store already, and I just became part of his iTunes/App Store family plan thing TODAY...the App Store still says buy for $199 and i'm running OSX Mojave 10.14.6 & App Store says it requires 10.15.7 or later I'm in the process of developing thing (I'm not sure what to call it, maybe you could help me with what exactly a thing including all this stuff would qualify to be; an Online Enterprise?) which will include a Social Media Presence, Podcast, a Youtube Channel (with a Patreon campaign), a subscription website (with exclusive relative content, forum, chat, etc...)

so, is there a way I can download the software my dad already paid for? a version that will run on OSX Mojave? I already have all the necessary hardware; Scarlett 2i2, Senheiser Microphone, 4K Camcorder, Studio Lights, all that stuff...

Technically, you need to log in to the App Store with the account that owns the license to download and install Logic on that Mac.

Legally, you may want to make sure that that both your dad and yourself can use the software, I'm not 100% sure what the EULA says on that point.

In the App Store you need to get to the screen that lists "Purchases". In 10.15+ you click on the user id at the bottom left. The "Purchased By" menu at the top right should allow you to select your father's AppleID. Scroll to where you see Logic and download.

No idea what it looks like in Mojave.

Family sharing is fully supported for Logic, MainStage, and friends