1. Ag and Timber is a sales tax exemption for some categories of goods bought to support production of agricultural goods timber
2, Ag use valuation, as stated previously, is not and exemption. It is a reclassification of the value of your property based on its ag production potential instead of fair market value. You actually pay the same taxes and the same tax rate, but on a dramatically lower value.
3. You have to be in ag production for 5 years before you see the valuation applied.
4. You have to be classified as ag for a period of time prior to transitioning into wildlife management. Not sure the time requirement.
the single best resource for all of this info and any legal topics surrounding ag in Texas is Tiffany Lashmet.
She works for AgriLife and you can find her stuff here:
Agrilife AgLaw BLOG