Hubs and templates

[Greygoose]

I've been reading here and see that a 'hub' is basically a nice place where you sit all your free sites at. Question is..

When I build a free site can I add 1 link back to my hub if it is on a domain seperate from the one my free site is on or should I strictly only have recips and sponsor links?

Also, regarding templates, I've made enough galleries to submit free sites for 3-4 months straight but I've also read I cannot use the same free site 'template' more than once. Is this true? Would I need 90 different free site designs? I'm not complaining, just want to know for sure before I give myself extra work.