Yes, you will need a parallel printer port on your computer to run VST 5/32 because it came with a hardware dongle for that… UNLESS Steinberg will allow you as a ‘legitimate owner’ to put your license onto a USB stick…which I understand that they then force you to destroy your parallel dongle. They actually suggest the USB license transfer in their site here, as a way to run VST 5 on a computer without a parallel printer port.
I’m not ‘aware’ myself of any way to determine if any particular song file in .all format has any means for you to identify what specific version it was created on. This does not mean that capability doesn’t exist, it may or may not(?) but I tend to doubt it. Maybe someone else can chime in on that. I don’t know for sure, but I would THINK that as long as you’re importing a .all file in a Cubase version that uses .all format, or can import .all files - SX3 being the last version to import .all files but uses/creates .cpr files - that it should work regardless 
As far as not being able to run Cubasis on Win XP, I don’t if this will work, but have you tried to run Cubasis in a Windows backwards compatibility mode? I used to do this several years ago for a couple of programs/drivers? (I forget what they were 
) and it worked.
In my opinion, VST 5/32 is still a very good program, as long as your set up can run it. The slightly less older SX3 is even better if you can get a hold of a used copy, and it will also allow you to import projects that were created with the .all format…in fact, this is the last version to be able to import a .all project. With SX3, a few of my friends feel this is the last Cubase version ‘they’ really will ever need. plus, with SX3, you don’t need a parallel printer port, so you can use a slightly newer machine & OS than that old thing you have laying around. Then again, VST 5 may be all you’ll ever need, depending on your own criteria. Both can be had cheap, if you’re willing to hold out for one to pop up on ebay or something.
Steinberg probably doesn’t particular like the above statements & suggestions, as they’re not making a new sale 