Is it true I can make a 2d side scrolling mmorpg with unreal engine? I heard on youtube videos that its possible, but i dont know where to start.
I haven’t used UE4 myself, but your question is too big. Break it down:
- Is it true I can make a 2d game with UE4?
- How can I learn to make a sidescrolling game with UE4?
- What kind of networking capabilities does UE4 have?
- Where should I start to learn how to write a server application that can manage a lot of players?
2d side scrolling, yes.
RPG, sure.
multiplayer, yep.
MMO? Maybe…
I don’t know how many hosts UE4 supports, but I have personally tried 25 hosts and it worked. I say you should go for it. If UE4 doesn’t support the amount of hosts that you desire, then you have a 2d multiplayer RPG, and that by its self sounds interesting to me.
Yes and no. UE4 doesn’t have built in support for the server solution you are going to need for an MMO. You can make the entire game and do great things with user to user networking but MMO architecture is going to take a lot of work outside the engine. Or maybe you could pull it off in C++ but good luck. 
yes, unreal engine grants you access to the very heart of the engine; its source. with it you can make anything your heart sets out to make all you need is the drive to learn what is needed to do it. (be prepared for a journey)
i say start from the bottom, make a 2d side scroller, and then jump into learning replication and research how mmo’s handle data/packets.(ue4 sadly is not mmo network friendly out the box, but it can do done) if you get stuck ask questions on the forum and answer-hub this community is pretty good at helping others
also if youc an spare the cash, i suggest looking into the mmo starter kit by codespartan, while its for 3d it has a lot of features you can apply to your own game (login authentication, inventory system, chat system,launcher and patcher, etc)
thanks i will look into that.