Soooo confused about "Obstruction"

[SactoBlue]

Tell me the answers to these questions ....... please...
1. Batter hits ball to outfield. BR rounds 1b only to be obstructed by 1b standing on base. BR chooses to go back to 1b because OF throws ball back in quickly but no play on them. My opinion, BR would not have made 2B even WO obstruction.
2. Same play as above only BR (in Blue's humble opinion) mighta/coulda made it to 2B if they didn't turn and go back. No play made on BR.
3. Same play as 1 above except a play was made on BR going back to 1st ...... tagged before getting back to base.
4. Same play as 1 above except a play was made on BR going back to 1st ....... no tag, back safely.