About licensing/trademark

[Nickfurious]

Hi guys.

Basically, I'm very passionate about expressing one's self into whatever you're wearing. I've been designing shirts for other people/small start ups for 8 years now and even though I've been doing it that long, I haven't really read nor understood any legal stuff about it.

I want to start my own company that showcases villains as the main characters on my design. Like bring to light what they're about or what they represent. Recently, I've come across Riot's page that tackles their licensing that can be found here.

http://www.riotgames.com/legal-jibber-jabber

After reading the post, I've tried Googling other riot inspired clothing stores online, and I've seen that they're not licensed by Riot.

Now my questions are:

Is it okay to just do the designs and don't mind these legal jibber jabber like these other online stores do?

Should I also do the same for characters from Marvel, DC, etc?

Is there a limit before they notice or like take actions if my business becomes successful?

Is there a way for me to be 'safe' from charges, like alter some features of the characters (change color, appearance, etc)?

Can you site other companies that did the same, got away with it, and became successful?

Looking forward to your replies

Thanks!