@Summer125 It seems quite odd, I couldn't explain where the guest would get the idea you have anything to do with the other property. It may be some sort of scam- if you clicked on that link, it may be some way to hack your information.
What I would do is just message back saying that you only host the property you list and aren't a co-host for any other place, so you are confused by their Inquiry message. Then see if you get a reply and take it from there (post here again if you still need advice). If it's a scam, they won't even answer, because all they were trying to do was get you to click on the link.
Don't worry about declining- this is an Inquiry, not a Request. Don't confuse the two- they are dealt with differently. There is never any reason to decline an Inquiry and every decline lowers your acceptance rate. With Inquiries, all you have to do is message back within 24 hours- you don't need to either pre-approve or decline. You will get pesky reminders from Airbnb to Pre-approve, but you can safely ignore those.
A Request does have to be either accepted or declined within 24 hours, although if it is inappropriate in some way, if you can convince the guest to withdraw their request, you won't have to decline it.