I don't really have any advice but to say that ALL kids go through these stages and that we've def all been there.
Hell my girls are 2.5 & 3.5 and they both still get into things.

Regarding the milk, can you get a lock put on the fridge? We had to do this with DD1 as she would get all sorts of random things out and either spill or eat them.
You can buy baby gates that actually have a gate built into them so you lift a little handle and you get to walk through rather than jumping over, it might be worth looking into some of those.

I know it's a PITA but can you get her to 'HELP' you when your doing other things, DD1 loved thinking she was helping and it meant i could keep more of an eye on her, it made it so much easier when i was PG with DD2 if DD1 was happily joining in.
I also found i had to engage her more, i had things to do YES but she needed my attention also and no matter how fat & tired i was (being PG i mean) i had to realise that she NEEDED that attention.

Can you set aside a time of day that is for reading, playing or craft that she KNOWS she will get at roughyl the same time every day, if she's naughty then she doesn't get to do craft etc.

I also agree with her having to help clean up her mess, DD1 has on numerous occasions been made to clean the carpet or the walls.