Ok, so I was about to complete "The Molecular Level." I had abstained from all spoilers involving the fate of Shaun, so I didn't know what was coming next. I was expecting it to be something like the Terminator shooting up the police station. I get in full battle rattle, with power armor, minigun, missile launcher, fat man, all that good stuff. I honestly expected all Hell to break loose. You see how wrong I was. Anyway, the logical choice, going off that presumption, would be to enlist the Brotherhood's help with this, considering they have an army of knights in power armor, vertibirds, and a giant freaking zeppelin. So, I go into the Institute, give the datatape to Proctor Ingraham, do a couple missions. Then it dawns on me that at this point the game is no longer on a specific track. I go on the wiki, and find out that eventually you have to pick a faction. I'll get to that eventually but right now I'm milking the side quests for maximum XP and rewards.

For anyone who is going to say tl;dr, here's my question:
Can I still get the Minutemen ending? I tried talking to Preston and Sturges, and they don't tell me anything aside from the normal settler/companion dialogue. I saw something about getting the datatape back from Proctor Ingraham, but no dice. But, that may be because I am currently on the mission "Liberty Reprimed."

Second question: Is it possible to have several separate, parallel, save files? Once I run out of the side missions I would like to play as each faction, but I'm too cowardly to fool around with my current save file and would rather ask a Hard Knocks Alumnus than enroll myself.

Edit: I neglected to mention this is on the XBox One.

Minutemen are not really hostile to anybody, but everybody else is to each other. If you have give BoS the tape then you are probably locked into either Institute or BoS on this playthrough. Once you play out this you can go back to a pre branching save and play though with the other factions. Shot of copying your saves into a folder there is no way currently to identify your saves.

Well, darn on both accounts. Thanks though.

I think you can, you just have to get the institute off side and MM quests open up. IIRC correctly.

And yes, you can make multiple saves,