can you use purdue vpn without being on PAL3.0
That’s the whole point
Yes, in fact PAL3.0 is the only network that you shouldn’t need to use it on. Its whole purpose is to give you access to things that you would otherwise have to be connected to PAL to access. Do note that it only affects Purdue-related traffic so it is not useful as a general purpose VPN.
The purdue VPN provides no extra functionality whatsoever