Were mitzvos m'd'Oraisa kept/performed in the times of Tanach the same way as today?

Although there are some times rabbinic disagreements regarding certain traditions and how details of certain Torah mitzvot were observed then (and some of those arguments still "hang" until today), the answer is clearly: Yes. For example, you can find on the web photos of the tefilin found in the Dead Sea Caves and Massada is identical to our tefilin (layed on the arm and head, made of leather, black, square, the same 4 chapters written on parchment, wrapped in sinews etc.), and they are most (!) of the way back to Sinai, and even closer to Sinai than they are to us! (about 2/3rds of the way back to Sinai- 2,000/3335 years)! The alter built by Joshua which Prof. Adam Zartal and his archeologists from Haifa Univ. found by Shchem between Mt. Eival and Mt. Gerizim, is the the only alter dated from that Canaanite period in Israel which has only ashes and bones of kosher animals, and the same ramp and other details described 1,500 yrs. afterwards in the mishna and studied to this day. We do find in Judges and Kings that in certain generations Jews disobeyed the mitzvot, sometimes even doing idolatry, but Megilat Ruth which we will soon read on Shavu'ot shows how leket and other agricultural mitzvot for the poor, yibum, chalitza, chessed and other mitzvot were actually "lived" and observed in the times of the Judges (about 3,000 yrs. ago). Similarly Shabbat and holidays like Sukkot and Pesach are mentioned in the prophets as being observed, and archeological mosaic and coins show lulavim and etrogim, menorahs etc. Many artifacts and texts have not survived, but those which do and are constantly being uncovered, show that those mitzvot d'oraita are generally described as we find in the mishna (1,800 yrs. ago), and which we observe until this day.