As you say, deffo not a doctor here, but will try for you, OK?
This reads to me that you have four lesions in total - three in your brain, and one in your spinal cord (neck region).
Reading from this alone, it’s not a diagnosis of MS (I’m not sure if you’ve already had a diagnosis separately), but someone with these findings would be at higher risk of MS - but might be lucky and not go on to develop it. Or, more rarely, have a different disease that causes demyelination - but MS is by far the most common.
No, you can, and usually do, have multiple lesions per relapse. Four is not actually a huge number, and could very likely all come from a single relapse.
I had six brain ones and at least one spinal one when first scanned, and was informed that was actually “not bad”, as it was not uncommon to see patients my age (44, as I then was) with literally dozens. So don’t get too hung up about the numbers game. Four is four too many, of course, when what we really want is zero - but it’s not at the crazy end of the spectrum.
A normal MRI without contrast cannot tell whether the lesions are recent or old - it can only see they are there. An MRI with contrast can tell the difference between active (current) lesions and old ones. If you had a mixture of active and inactive (old) lesions, it would suggest they came from at least two different relapses (one that you’re having now, and at least one other in the past). But it still can’t tell how old the old ones are, and whether they arrived from a single relapse, or several.
That’s why, at diagnosis, they can’t tell how long you’ve had it - they can only go by your own reports of when you first started having symptoms. If all four were active now, it could suggest it’s your first and only relapse, and therefore isn’t “multiple” yet, and can’t be called MS.
Hope this helps!