Yes you are legally an adult but you are also living under your mum's roof.
I say this as an 18 year old who had very strict parents which lead to some situations that would not have happened had they been more sensible.
Unfortunately I think the phone access is reasonable, if you are accessing porn and come across something illegal (you might not realise it is) it is your mum's house that is going to be searched by the police.
Can your mum sleep if you are awake? If she can't then you are keeping her awake until 2.00 am sometimes.
You probably need a long talk with your mum (and dad, from the way you have written it seems they are separated).
Think what restrictions you could have if you were in uni halls or lodging in a private house.
If you were in uni halls you would probably have electronic access to the building but possibly not the room, that means the uni can record who is in the building. You would also have room inspections a couple of times a year.
Make a list of things that you think will work eg if you are at home at 10.30 the outside doors are locked for the night and will not be opened until morning.
If you are out then what will you do do that your mum knows you are home (think about a fire situation) maybe have a hook somewhere where you will put you keys.
Things you will not do after your mum is in bed. I'm thinking cooking, lighting candles, things your mum will worry about.
Don't forget to include your parents in the conversation. What worries them?