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I'm good in JS(but more functional programming and less OOP). Also HTML, CSS, Sass, Jquery, Bootstrap... you get the point. I know only basics of PHP and little bit of ReactJS.

So no problem for you either. The only decision to make is, will you query the blockchain or query a database with blockchain data.

Blockchain is slow in query but uptodate. For database it is the other way around.

Sweet! Languages of the past include Perl, Visual Basic.NET, SQL and some Java. Just a couple days back I started on C# (console apps, Windows apps and a bit of Unity :P).

Seems like you have enough knowledge to get an app based on the blockchain to work :)