From whom, how, and why were the following lands acquired: louisiana purchase, oregon, texas, and the mexican cession

Louisiana was purchased from France and was bought to access the Mississippi River. The Mexican Cession occurred in 1848 and was acquired because of the Treaty of Guadalupe Hidalgo after the American victory of the Mexican-American War. Oregon was acquired in 1846 and was acquired from Britain. Texas annexed itself from Mexico in 1845 and became it's own country for several of years, before joining the U.S.

arresting and exicuting citizens

you can't, there's no way sorry