Alright, so a friend of mine gave me a Pro license of his to activate, in a license file .lf ( not sure if thats the extension )
and said that it needs to be unity 4.1.2f1 for it to work. I have unity 4.1.3 and it doesn’t work.
Is the problem with the license or do i really need 4.1.2f1?
Did you just seriously ask this question?
Do you even know what a license really is for?
Read this page and while reading carefully it should be pretty straightforward why this isn’t working.
And certainly not least, learn “the rules”. (as in, respect license and software terms.)
I’m going to extend the benefit of the doubt and assume that you honestly did not know that what you were attempting was piracy.
That being said, Unity Pro licenses are purchased on a per-user basis at $1500 per license. Your friend’s license is only applicable to your friend. In order to use Unity Pro, you either need to activate the One month trial (which expires after, you guessed it, one month), purchase a perpetual license for $1500, or opt-in to the newly released Pro subscription for $75 a month for a period of no less than 12 months.
Alright, alright calm down i didn’t know!
We’re both new to this.
Though it’s hard to imagine since unity’s normal version is advertised as free very clearly and from the moment of first use youre already asked for a pro TRIAL which already suggests that its not free…
I’ll just take a guess that you’re very new to licensing in general, and want to warn you strongly up front because pieces of software like modeling suites are normally quite high in prise (apart from i.e. blender, which is free) and might make piracy look attractive. But bear in mind that its possible to get in a lit of trouble when i.e. it would be discovered youre using assets created by illegal means.
Imagine in time building your experience and running into trouble because of piracy/licensing issues. It could mean you’d technically have to create those assets all over again, potentially in a whole different program needlessly steepening the learning curve.
And in contrast; how would you feel if you released your first game with a free demo. But instead of purchasing the full version for 10 bucks each people are simply downloading and cracking the game, would make you at least a little angry wouldnt it? 
When starting to dabble in Game Development i’d say its the best time to keep an eye on such things. Even though i can safely say i’m not an angel either (i had one suite of software which i only purchased after 2 years of use (due to its high price even))