You will have multiple different answers, but if you can afford it > go for it, if not, you have some templates to be used and focus on your product

It depends, but yes you can do everything by yourself, as everything can have ui. It’s just based on your requirements what you want to change and you could build admin panel based on those

That’s what some of my friends and I saw as a problem that requires to be solved. It’s important to choose right tech for the specific project, you cannot use just one.

And for the OP, as you probably will built social app with some geolocations (based on description I assume it will) have graph for database, and not some relational db, as you will need a lot of different information to catch in one query and the problem if someone choose for you relational db will be something to solve when scale