I mainly use LINQ for CRUD purposes instead of SQL, should I also learn hard coded SQL or just stick to LINQ EF?
It's always a good thing to also know ADO.NET (in combination with stored procedures or not). There are still quite a lot of applications out there which don't make use of an ORM and likely your manager also wants to put you on either maintenance or upgrading older applications. So consider it a plus/bonus for yourself and possibly getting hired if you do know it.
I suggest you take a look at this article: Using ADO.NET with SQL Server.
Is it a good idea to start learning MVC now and use it on all my future projects or is it too early for me?
The wider your knowledge the more attractive you become for your employer. If you took the path for ASP.NET (Webforms) then certainly also take a look at MVC, Dynamic Data and WebPages. You'll benefit from the extra knowledge.
Do employers favour MVC over WebForms when recruiting junior developers?
You'll have to look this up depending on the geographical area where you want to work and do a case study. But given the fact that you want to broaden your knowledge and learn the different flavors of ASP.NET an employer should be happy to hire you. Besides, all flavors all build on top of the ASP.NET core framework.