Was the Apostle Paul A Sabbath-Keeper, after He became  A Christian?

Why was the Sabbath NOT given to the New Testament Church, as an Ordinance to be kept?

Was worshipping weekly on Sundays introduced by Constantine or some Pope, as our Sabbath-Keeping friends teach?

Is worshipping on Sundays simply A New Testament, Heretical Tradition? Or Is It GOD-Ordained, and of Old Testament Origin?

Why do informed Christians worship weekly on Sundays? And, can worshiping weekly on Sundays ever be the Mark of the Beast?

" He that saith, I know him and keepeth not his Commandments, is a liar, and the truth is NOT in him" (1 Jn. 2:4).

"If you love me, keep my commandments" (Jn. 14:15)

"For NOT the Hearers of the LAW are Justified, but the Doers of the LAW shall be Justified "(ROM. 2:13).

"The Son of Man is LORD also of the Sabbath Day" (Mk. 2:28), (Matt. 12:8)

" The Sabbath was made for man, and NOT man for the Sabbath" (Mk, 2:27)