I don't know if I should answer this question or not???
If testing for this type of thing and doing the testing properly - knowing what you are doing, then you can determine if the neutral is connected or not.
But if you don't know what exactly is going on with this testing, then quite easy to mess up your wiring, electrocute yourself, or damage your test equipment.
Basically all neutrals connect together at the main panel. So if measuring voltage from a hot from another outlet to any neutral which is connected, you would get a voltage.
Or if the MAIN POWER was turned off, and you were using a continuity tester or an ohm meter, and measuring from another neutral to this neutral, and it was connected, then you would get a reading. (Using meters for these tests with the power on can damage the meters.)
The problem is this is a "circuit" with possibly many things interconnecting. One light bulb on this neutral and the switch on would connect the neutral to a hot. Then that hot may travel to another "on" electrical device and "see" a neutral from that device. So in testing, the neutral may appear to be connected, but only may be connected via the light bulb and hot (after you had disconnected the neutral). So its necessary to fully understand your readings and what is going on with the wiring - what all is connected to what.
Then with K&T, the wires are the same colors. So you need to determine which is hot and which is neutral.
So before working on K&T, you should have a full understanding of how to use a multi-meter and how this meter can be damaged if not used properly. A full understanding of K&T wiring and what possible connections may exist. And a full understanding of electrical circuits and how to trace out circuits.
Basically this is advanced stuff.
The easy way to do this is to cut holes in the walls and see what wires are going where and if any wires are spliced in the walls, then heading off somewhere from there.
Then what goes in, and what comes out! -> If you go up in the attic and there are two wires going down a wall. And on that wall below there is one wall switch. And you remove that wall switch and inside the box there are two wires as well (and no other electrical boxes on that wall), then it would be logical to assume that those wires only go to that switch. But don't bet your life on it! You might tear out the wall or cut a hole in the wall and see wires spliced to those wires in the wall!
I saw this recently twice! A short run of K&T of about 6 ft. from a wall switch to a bathroom wall light fixture. Should be just two wires running to the light fixture right? Nope... In the ceiling there was a splice into the wires and another wire leading off a few feet and then cut and taped. Then in the wall there were two old twisted lamp cords spliced into the same wire and these were leading off to either side of the light fixture, then cut and taped.
So at one time a ceiling fixture was installed and then removed. Then there were wall sconces installed and then removed. Wires left in ceiling/wall.
So no telling who did what at any time in the past.
Tools for testing are...
Turning everything on/off to see what is on a particular wire run. Disconnecting the wiring at a certain point and see what no longer works.
Using a voltmeter.
Using a continuity tester.
Using an ohm meter.
Using an inductive wire tracer with signal generator...
http://www.professionalequipment.com/extech-tone-generator-amplifier-probe-kit-40180/wire-tracer/
Testing from the hot of another circuit with a long length of wire.
Testing from the neutral of another circuit with a long length of wire.
Visually tracing wires.
Cutting holes in walls/ceilings and using mirrors/flashlights to see what is in there.
Removing switches/outlets/fixtures and seeing how many wires are in the box.
Disconnecting a wire at both ends and measuring for ohms/continuity.
Or rip out all the walls and ceilings!