It's kinda stupid, but I want to do it since my warranty's almost up, and when the triangle happened before (with the whole Air UI scenario), the Nokia care I visited seemed to replace the case and glass for free, and that's what I want to do (since I bent the USB port but they say I have to wait for the warranty to be finished :\)

So how do i force it to go into this yellow triangle that won't allow it to boot? (unlike openmode warning, which I disabled)

If you bent the USB door, you can purchase a replacement for somewhere around $10 and swap it out yourself. If the actual port is bent, that's probably a much more serious problem.

Also, isn't the warranty 1 yr long? It shouldn't even be possible for the warranty to have expired for anyone yet...

Are you sure that they didn't just replace your whole phone as a gesture of goodwill, as opposed to just replacing the glass and case?

I'm assuming from Air UI scenario your previous phone was just bricked right? like software.....
If Nokia Care said you have to wait until the warranty is finished to get it fixed..... well that just sounds fishy, maybe that rep was a clown.

Besides when your warranties over they'd be like, too bad you have to pay for it, if you bent your USB port, even within warranty, they'd say too bad you have to pay for it.

Besides that, if it's the port that broken, they'd discover that while trying to unbrick your phone from the forced yellow triangle, again they'd say too bad you broke it so it's not covered by warranty, and then you'd be up **** creek with a bricked phone that can't be unbricked because your USB port is broken.

These guys sell the USB connectors for 3€, but I'm guessing it's a tricky little solder job so you'd probably need mad skills to replace that yourself.
http://www.klc.fi/fin/tuotteet/Nokia...et-ja-varaosat

If Nokia Care wont give you a quote to pay for the replacement USB port, take it to a Nokia authorised repair centre so that you can keep your warranty, they'll give you a quote to fix it, unless you want to wait at least 5 months without USB connection, just for the warranty to expire so that Nokia Care can say too bad it's out of warranty.

I still have USB connection if I force the cable in at an extreme angle and I have to hold it in (experienced with N8 before, where my brother knocked the phone while it was still connected, bending the port a bit)
And the cover is slightly bent too, something that really ekes me out.
I'm not really good in fine-handling tools or taking apart my N9 (I have shaky hands)