Q: El Capitan - Login Screen spinning ball problem.

There may be a hardware related problem with the startup issues

you have experienced; if the main startup drive is getting full, or

if there may be older non-compatible kinds of software installed.

Have you tried to see if Safe mode startup can get past the initial

issues so you can further troubleshoot the system? You can expect

to have to enter Admin password as part of the slow start in Safe

mode or safe boot startup. Hold the shift key after start tone, &

keep holding until you see progress bar, then login to see desktop.

•Try safe mode if your Mac doesn't finish starting up - Apple ...

What is safe mode? Safe mode (sometimes called safe boot) is a way to start

up your Mac so that it performs certain checks, & prevents some software from ...

support.apple.com/en-us/HT201262

You can use Console utility to view various system logs, OS X Recovery

as a startup method to see what Disk Utility can tell you. You can repair

a boot drive only if it is unmounted; so the recovery startup allows this.

A report of basic startup software and system specifications can be obtained

by using the Etrecheck utility that generates a report you can post in ASC.

Etrecheck - https://etrecheck.com/#about

If there may be any evidence of adware, or odd extensions added to browser

or other malware-like bits, you could locate and learn how to remove them.

Performance issues can be induced by installation of an antivirus; ineffectual

as advertised, these things only slow down and sometimes damage the OS.

In any event...

Good luck & happy trails!

So, starting up in a reduced version of OS X where certain parts

that may have issue, does nothing different for your Mac; and

you are saying that any attempt or incomplete boot or start up

is equal no matter how it was arrived?

I'm saying you can troubleshoot a normally acquired startup up

issue in Safe mode because it also checks files & can do repairs.

Also you could then troubleshoot by adding items or removing

them from the startup file (associated with user account) or also

try a second user account to see what if anything works just fine.

But once you are to the point where Terminal command line is

part of the diet, the OS X may just need to be reinstalled on a

known-good and correctly partitioned hard drive. And the other

startup method can include a path suggested in OS X Recovery;

this reveals the other utilities to direct attention to deeper repair

and/or re-installation. Be it from one of two possible archives,

either the most recent OS X, or the internet recovery of original X.

{If there were encrypted system files or file vault, the matter may

involve other troublesome routines or methods to get into there.}

If you cannot get past the login screen, even with Safe mode, then

try to see about re-installing OS X from the recovery startup. Of

course it helps to be able to start & get past the login screen.

If you had an external drive with clone of present OS X, that may

allow you to get past any actual system issues on internal boot HD.

Good luck & happy trails!

Yes, does sound like you've gone more than the route, and a few alternatives

that should have gained some traction toward resolving this issue. And it is

beyond the usual kind of issues that people have faced on rarer occasion...

Hopefully someone with experience in this matter can see something else

to try, so you can get past the stone wall in the way of progress at this point.

I've held off on upgrades to my Late 2012 Mini i7 2.3GHz; it shipped w/ 10.9.

And find 10.9.5 is relatively stable with few realized small bugs & pesky issues.

This is my newest Mac and latest OS X version, of four working models here.

Sorry to not be of any help in this matter.

Good luck with the path ahead...!

With abysmal internet, slow speeds, ceilings on download, higher cost per GB

my hoped for use of the Mini (clearance item new at Apple online special deals)

two years ago has not been worth it so far. I'd missed upgrade past Mav 10.9.5

and didn't get earlier questions answered. I do have a download of El Capitan,

with some reservations on actually installing it. Not sure of what macOS Sierra

really means or what level of unnecessary fluff it brings. I don't need most of the

Cloud-based stuff because of internet access issues; hard enough to get updates.

{So I haven't anything that would need to share -- between macOS, or an iOS.}

Used to be when I was able to repair hardware on various older Macs, I also figured

out how to upgrade them in both software & hardware beyond usual limits. Then I

gave them away, each a working kit; to persons who could not afford one. Like me!

So I'd best not further clutter your thread.

Best regards & good luck!

Sleep – Slow Wakeup/Requires Reset

Sleep - Wakeup