add review comment

Author: crandmck

docs/manifest/reading/legacy.md

@@ -11,7 +11,7 @@ Old manifests may contain these kinds of deprecated ingredient data:
 - V1 ingredients, with label `c2pa.ingredient`.
 - V2 ingredients, with label `c2pa.ingredient.v2`.
 
-<a name="question"></a>
+<a name="question1"></a>
 
 <div class="review-comment">
 What should we say about reading v1 and v2 ingredients?
@@ -21,6 +21,8 @@ What should we say about reading v1 and v2 ingredients?
 
 Existing manifests may contain two versions of actions: original v1 actions, with label `c2pa.actions`, and revised v2 actions, with label `c2pa.actions.v2`. While a v1 action is fully specified in its actions array, a v2 action may either be fully specified in an element of the actions array or it may be derived from an element in the templates array with the same action name.
 
+<a name="question2"></a>
+
 <div class="review-comment">
 What should we say about reading v1 actions?
 </div>

docs/manifest/reading/validation.md

@@ -5,6 +5,14 @@ title: Validating manifests
 
 Processing an asset includes [validating the manifests](https://c2pa.org/specifications/specifications/2.2/specs/C2PA_Specification.html#_validation) in the associated manifest store. During validation, errors can occur in the active manifest and in ingredients.
 
+In the latest version of the SDK, 
+- Builder performs validation by default, so you can't create an invalid manifest.  Previously, the SDK was permissive in this regard.
+- Validation is much stricter
+
+<div class="review-comment">
+Need a high-level summary of full validation, what we're looking for, etc.
+</div>
+
 ## Validation errors in manifests
 
 When you load an asset, all the manifests in the manifest store are validated and any [failure codes](https://c2pa.org/specifications/specifications/2.2/specs/C2PA_Specification.html#_failure_codes) are assigned to the `validation_status` array. Inspect the array to find the validation errors. 

docs/manifest/writing/assertions-actions.md

@@ -26,12 +26,16 @@ The standard form of an assertion in a JSON manifest is:
 ]
 ```
 
+:::important
+Every manifest has to start with either an opened or created action, which has to be the first action in the manifest. Each of these actions need to have an associated ingredient.
+:::
+
 ### Changes from earlier releases
 
 Changes include: 
-- `c2pa.data_mining` > `cawg.data_mining`, etc. were renamed, with xref.
+- Old training and data mining assertions `c2pa.data_mining`, `c2pa.ai_training`,  `c2pa.ai_generative_training`, and `c2pa.ai_inference` have been replaced by [CAWG training and data mining assertions](../writing/assertions-actions.md#cawg-training-and-data-mining-assertion)
 - `SoftwareAgent` is a [ClaimGeneratorInfo](../json-ref/manifest-def.mdx#claimgeneratorinfo) structure instead of a string. 
-- Ingredients are now V2 ingredients
+- Ingredients are now V3 ingredients
 
 #### V2 actions