A few newbie questions about the google play store, and rooting my phone

I remember a while back hearing about custom google play store APKs, are they still a thing? And if so, could someone explain them to me? (Or just send a link to them)

I've tried Mobilism, but the search is locked behind a login and their activation emails aren't reaching my inbox.

Could someone help me root my phone?

I've never rooted phones before, and I can't find any trusted information on how to root my specific model of phone.

I have a Samsung A03s, please ask me if you need information.