@duhashostka,
Quote: Is this sentence "I was typing from 2 till 4" correct (Past Continuous)
Yes, it is correct and it is commonly used.
Quote:When we use Past Continuous, we don`t know when the action started or finished.
We do know if the times are specifically noted, Duhashostka, as they are in your example.
Quote:I think we have to use Past Simple - Duration in Past - "I [was] typed from 2 till 4". There isn`t any continuation of this sentence.
We use both the PC and the SP with time adverbials that are both specific and general.
I was typing/I typed from 2 to 4/all afternoon/for a long time.