In general, you should be playing with a 100bb stack ($2) rather than a 50bb stack ($1). You'll have more opportunities to learn postflop play with a bigger stack.
You have KQo in the SB. It folds to the BTN and he min-raises to 4c and you fold. Instead of folding, you should've 3bet to 14c. He was clearly trying to steal the blinds. A lot of people open wide on the button and he could've had a hand as weak as K8s, A9o, 43s or 22 just trying to steal the blinds. You need to be contesting this because KQo is a strong hand, similar in strength to AJo.
You played fine, I would've done the same thing there.
Why are you opening to 4c? The only time you should be opening this small is if you're in a steal situation (on the BTN, for example). When you're in early position, you should be opening to somewhere between 6c and 8c (when in doubt, open to 3x from every position). As played, I like the fold to the 3bet shove.
With a 42bb stack from early position, you should be folding KJo. Even with a 100bb stack, this would probably be a fold, since you're in early position with a hand that's easily dominated by AJ, KQ and AK (common hands that will call a raise).
Postflop is a bit more complex, but I'll try to explain what I'd do: on the flop, you should be C-betting a lot larger, to at least 70% pot (13c or higher), rather than 8c. When you bet 8c into an 18c pot, you're asking people to float you with 2 overcards, a low pocket pair or a backdoor draw. When you C-bet to 13c or larger, you're putting them to the test. I'm fine with check-folding after the flop because it looks like the villain is slow-playing a set / full house, especially with you blocking the K of hearts which takes away a lot of flush draw possibilities.
If you were deeper stacked, you could have made a large C-bet here (about 80% pot) without making yourself pot-committed. As played though, you had to check-fold. Another example of why you should top up to 100bb.
This is... interesting. It's like you suddenly changed from being weak tight to being loose aggressive. There's nothing too horrible about this shove, but it does seem very high variance play and could get you into trouble if you make a habit of this. I'd prefer to just play with a 100bb stack and make a standard 3bet size to 20c. I'm liking the preflop aggression though.
Terrible preflop play... with a 30bb stack, you shouldn't be playing KJo at all, but if you are going to play it, you need to make a raise to somewhere between 8c and 10c to isolate the fishy player (the limp-caller), rather than allowing yourself to get squeezed. As played, I like the fold to squeeze.
I'm probably C-betting this flop to 10c then giving up, but checking all the way down is okay too.
With a 100bb stack, I'd be doing exactly the same as you: opening QJs to 6c in early position. But with a 31bb stack, this should definitely be a fold. There's no implied odds
with suited connectors when you only have 31bb and you're going to face a lot of reverse implied odds the times you flop top pair and are forced to GII due to your stack size, only to lose to a higher kicker.
I didn't go beyond hand 33, but you get the gist. You need to either top up to 100bb or change your strategy completely to avoid implied odds hands (QJs, KJo, 44, etc.) if you're going to be playing with a medium stack size. Also, you need to make larger bets postflop. Try sizing all your bets to 70% pot, rather than 40% pot.
Good luck! With due time, I'm sure you'll be able to crush 2NL and then you'll be looking back on this thread and laughing.