Browse Host has never been perfect. In LW 4 or in LW 5.
If you can't browse a host with LW 4, try in a few minutes & you might find that you can browse successfully.

I'm not sure how LW deals with a file with multiple hosts - whether it browses the host with the first file found or what. But you can only browse one host at a time.

An ultrapeer isn't a databank - just a person with a fast connection who isn't firewalled & is capable of handling lots of search traffic.

There were many 4.18 versions - you didn't say which version you're using.