Is it true or false that slugs have no noses?

Yes and no according to
http://velvetdragon.com/cyberslugs/realslugs.html


One of the most frequently asked questions about slugs is what the hole in its side is. The hole, located on the mantle on the right side of the slug, is the slug's pneumostome. This is like the slug's nose, and is the hole it breathes out of. The slug has the ability to close this hole.

First of all, a nose is not a hole in your body... that would be an olfatory organ but isn't a nose.
Second, the hole in the bodies of snails/slugs are not used to smell. They are used to breathe.
What is used to smell are the tentacles.
http://www.allaboutslugs.com/slug-and-snail-science/slug-anatomy/

All tentacles move independently, allowing slugs to look and smell in several directions at one time.

https://www.northcoastjournal.com/APRIL96/4_96_GAR.HTM

Their 'eyes' are at the tips of their antennae with which they also smell.