Can anyone point me to previous topics, websites of FAQ's that would anwser some questions about stacking and combining offers and awards?

I was wondering what awards/discounts can be combined (if any).

Example, if I had a free suite upgrade coupon, can you combine that with a 50% your stay, or a stay 3 nights get one free?

If you book a room using HiltonHonor points only, are you then unable to add any additional offers?

I tried searching the HHonors website, and past topics but couldnt find anything.

Thanks, and sorry if this is something addressed quite often.