Welcome. If you were going very slow and put it in 4th gear the car would've reacted. I don't see why 2nd gear would've caused it.
For your other question it depends. If I know a turn is coming up and there's no traffic I will start downshifting in to 3rd, then 2nd. If its a quick/last minute turn I will slow down enough to where I can go right from 4th to 2nd. Sorry, hope this makes sense. It's hard to type out driving habits lol
Most subarus have a safety lockout to where you cannot put the car in 1st gear unless you are completely stopped or going 5mph or so. In my 06 wrx, sometimes I can put it in 1st while rolling to a stop around 10mph. Sometimes it won't let me unless I'm completely stopped. It's hit or miss.