I have an older USB 1.1 device which I need to have 5 metres from a computer. I know USB 1.1 cannot operate over a 5m cable but USB 2.0/3.0 can. So if get a USB 2.0/3.0 hub, will I be able to connect the USB 1.1 device to it and use it on the end of the 5m cable connecting the hub to the computer?
Yes you can. A USB 2.0 hub (or USB 2.0 "sub-hub" within a USB 3.0 hub) will continue to communicate with host using USB 2.0 High-Speed signaling rate. To communicate with FS and LS devices, all USB 2.0 hubs have built-in so-called TT - Transaction Translator(s). The TT has buffers to hold fast-coming data, and then translate the data at much slower LS/FS signaling rates on downstream ports, autonomously. To communicate with TT, USB host uses so-called "split transactions", a subset of general USB protocol, which can check for completion of slow transfers using very short high-speed packets that do not take much of upstream bandwidth, saving it for other USB transactions. This is the whole idea.