Hi Tapeman, welcome to the forum. 
For the $25 GC you will have to tell us a bit about YOURSELF - eg how old are you, what’s your personality like, and what are you hoping to get out of pheromones?
As for your questions, they are good ones. I will try to answer them best as I can but it would be better to wait for more experiences users to come along and help you out there. 
The only health issues that I can think of are many allergies (to certain scent carriers, not really the pheromones) and build up. Some pheros such as -none need to be removed thoroughly, or they will build up over time and give you negative effects such as aggression from other males. However this one isn’t a health issue, per se. It is not recommended that you wear pheromones around small children - I think a good guideline is 4 years of age, but of course it would be highly inappropriate to wear overtly sexual mones in the presence of older children. Just common sense, really, but I thought I’d add that in there anyways. 
As far as I am aware, no, your body can’t become ‘addicted’ to them. Some pheros bring about self-effects and these may diminish over time, but artificially formulated phero products will only add to your natural signature, not replace. I think some of this is because you don’t ingest them.
Many users do report self-effects, although some don’t. When I use Instant Shine I don’t seem to get the instant mood-lift that I often read about, BUT my face muscles tend to relax, which means that my smiles come bigger, more naturally, and more often. It is a youtful, fun, feel-good phero, and hard to go wrong with, so I would definitely recommend trying it out!
Hope this helps a little! Take a look at the sticky on the forum to find out the criteria for that gift certificate
and come back with questions as you think of them 
Welcome aboard!