Restriction Enforcement Across Versions 

Server-side enforcement: confirmed identical 

The server-side enforcement layer, Classes/Hooks/DataHandler.php and Classes/Helper/RestrictionGuard.php, contains no TYPO3-version-conditional code. The same allowed/disallowed/ maxitems checks, in processDatamap_beforeStart() and processCmdmap_beforeStart(), run identically regardless of which supported TYPO3 version (^12.4 or ^13.4.7) a project runs. There is no known gap between them for this enforcement layer.

Related, but not a restriction-enforcement, difference 

Two other backend touchpoints do differ by TYPO3 version, and are easy to conflate with restriction enforcement because they sit nearby, but neither one decides what is allowed or accepted:

• The record-usage marking mechanism, Hooks\PageLayoutView (dead in the versions this branch supports) versus IsContentUsedOnPageLayoutListener (current), only affects whether a grid child is reported as "used" for Core's own unused-content indicators.
• The List module XCLASS, Xclass\DatabaseRecordList versus Xclass\DatabaseRecordList12, only affects how nested rows are rendered when nestingInListModule is enabled.

See Extension Points for both.

Scope of this statement 

This confirms behavior for the current codebase on this branch only, supporting TYPO3 ^12.4 and ^13.4.7. It makes no claim about restriction-enforcement behavior on other maintained branches of the extension; earlier branches maintain their own, independent file set and are out of scope for this documentation.