ToME: the Tales of Maj'Eyal

For example Range Amplification Device prodigy needs 10+ light radius to pick it from the list - what happens when I remove item(s) that allows me to have 10+ light radius? Say I go from 11 radius to 5 - is the prodigy going to be disabled until I get radius back to 10+? Or will it still function?

Same question about skills - if I put an item that boosts my requirements, pick the skill and then take off item - will the skill be disabled? Or will it roll back to the level where requirements are met?
Ex: Thick Skin needs 50 Con for lvl 5.2, what if I take off items that gives me 50 Con, will it jump down to lvl 3.9? Or will it stay at 5.2? Or will it be disabled completely?

In general prerequisite stats are only needed to qualify. Once you have the talent/prodigy selected you can go beneath the required stat and not lose access.