Anyone know what this yellow square with letter "i" stands for?

That's a warning light. This is also telling you your tire pressure is low.

When u swapped ur wheels did u have your tire pressure sensors swapped over to the new wheels? If not then thats ur problem. If u did swap them then either ur tire pressure is low on 1 or more tires, or they need to be relearned to the car (reset).

Got it. Thanks guys. I put on a new set of wheel / tire but didn't get TPMS sensor as this is my winter set.

If you pull the center lever towards you on the set of three levers on the lower left (7 o'clock) on the steering column it will tell you what the "i" is for in the center LCD display. My guess is it will be something about the TPMS if you didn't swap the sensors with your snow tires. Mine is on all the time along with the other warning light that is on in your picture showing the tire cross-section icon and "!"

That's the one. The other two toggle back and forth between digital speedometer, driving time or nothing. The middle one just tells you what the "!" is about. it seems like a lot of stuff that doesn't do very much. I drove a loaner 2017 Forester and those same little levers operated the upper center console LCD display. I wish my 16 WRX did that.

Thanks man!

That i is like a 'general' ennunciator light telling you that "something" is not right somewhere. You then have to look for other lights or indicators or guages to find the specific problem. The tire symbol at the bottom is the one telling you your TPMS is either not working or thinks there is a low tire in this case. The "i" is called an 'information reminder" on page 3-36 of my owner manual.

Didn't your WRX come with a manual, in the glove box?

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"Hmm what's this little button on the steering wheel with a matching symbol do" hahaha.

My question is what does it mean when it comes on randomly by itself but in the color red?