Need help with trash segregation

I moved to Japan a few days ago and after sleeping through my jetlag and eating out, I now need to segregate my trash and I’ve watched a lot of YouTube videos and read the manuals, but it’s still pretty confusing to me for some items.

I need help in understanding which category would these items fall in?

1.) Covers of phone case: The outer covering of the box that phone came in.

2.) Wrapping plastics of phone: There’s wrapping on the phone. Where will that go?

3.) Used tea bags

4.) Covers/boxes of packed lunch and instant noodles.

I’m in Chiyoda city and I’ve put these like this so far:

1.) Covers of phone case: Plastics
2.) Wrapping plastics of phone: Plastics
3.) Used tea bags: Burnable
4.) Covers/boxes of packed lunch/instant noodles: Plastics

How wrong is my understanding? Can please someone help me out with this.

Also, where can I buy these trash bags? I have 0 Japanese knowledge right now and I couldn’t find the trash bags with distinct colors at shops nearby.

What can I ask at convenient stores to buy these? How do you all segregate your trash? Like do you have 4 different bins and dispose trash in them and take them out or something else?