What would you do...

Are you sure that your son is the one opening it? Because both of mine know how to open all the child looks we have. And my second figured that out shortly after turning 1 by watching her sister 🙃

As for medicine you could look into a lockable cabinet or storing it high. Otherwise it is mostly about repetition of explaining the danger etc. Unfortunately it takes quite some time for them to understand it

It really might not be your son my mom would punish me and my sister for drinking all the juice in the fridge saying my brother couldn’t open the fridge or drink and one day she was sitting on the couch and heard something in the kitchen and it was my 2 year old brother with the fridge open chugging milk and she felt so bad. Also can you baby gate up? I baby gate the entire kitchen off and bathrooms and bedrooms

What kind of locks do you have? Changing the type might make a difference. You can try taking toys away or you can try more structured toys like tv games that get them all active at the same time. Sounds like they’re bored. My 2 and 3 year old start getting into stuff when they get bored and it’s usually when I’m around the house doing chores.

Kids don’t really respond to the “feelings” talk the way a lot of people think they do. What is the reason for the behavior? Are you giving more attention when he breaks this rule? Maybe he wants your attention. Does he desire the items he can’t have? Maybe put it up high or out of sight (out of mind). Boredom? Look up easy games to set up ahead of time for independent play.

Explain the boundary 1 time. “When you do (this), then (that) will happen”. Make him repeat the rule. "Listen carefully."
"Can you repeat what I said?"
“Now tell me what happens when you disobey?”

Now you know he understands. No excuses not to do a consequence which can depend on several factors. Time outs can be very effective but only under very specific circumstances.

After the consequence, Put the responsibility back on HIM. “Was that a wise choice?”
“What do you think should happen next time?”

Personally I absolutely would not tolerate the yelling. “I listen when you speak respectfully. Try again”

Try listening sticker chart! It’s important to stay positive and encourage positive behavior. Tell them if they listen they will get a sticker. The sticker will equal rewards if they don’t listen they lose a toy anytime they don’t listen. Pick up a toy say bye your last playing time with this toy for not listening and put it up high.
Encourage them to close the doors that’s what I had to do with my son when he learned how to open the child locks, I was taught to encourage him to close them and put more emphasis on him, helping me out, closing the doors, the trash everything that worked for me however every child is different.

*Lost it for not listening