Licensing a finished product, Legal steps, MegaGrant application for a finished product(for updates), Advertisement Assists.

I’m about to launch my product on the market but I have several questions.
1- What are my legal required steps needs to be taken into account before launching the product on the market(company established)?
2- How can I license and protect my product(does Epic Games license the game on the behalf of both Epic Games and my company or are we supposed to license on our own -or need to take any other legal steps to protect(if so what are those steps)?
3- I totally have NO IDEA how to get my game advertised, does EPIC GAMES give any support on this issue(maybe some youtubers with any agreements to get in touch with)?
4- If my project fails(which I totally have faith in) I don’t think I can financally hold long yet I have many update ideas to do. Can I apply for megagrants after launch(in order to get those update ideas alive and pay for some advertisements)?
5- Can I also put my game on steam too?

It is getting late in my country(I mean early) so if those questions have already been answered before sorry for your time but I really have almost no time I need to get some sleep and head back to the project (I know all of you guys understand)
Thanks in advance.