Jesus Christ, the guy asked a simple question...
The Krink receiver is the same as the AK-74 and it fires 5.45mm, but there are extensive mods to it:
shorter barrel
unique muzzle booster
unique combined gas block/FSB
unique front trunnion
unique handguard retainer
unique handguards
unique rear sight block which really becomes the "hinge block"
hinged top cover with flip sight
edited to add short gas piston
Those are the main differences. It uses folding stock hardware which is pretty common but there are particulars in stylistic features. The very earliest AKS-74U's were built by Izhmash and these were sort of non-standard... some of them even featured optics rails on the left side.
The vast bulk of the production got shifted to Tula and the design became finalized with no optics rail, thr "rolled-edge" steel stock, the shiny plum PG and of course the star-shaped Tula arsenal markings. There is also a unique sling for this firearm, as well as a specialized canvas mobility or "drop" case.
The handguards eventually evolved from laminated wood units with cooling slots to models with a straight edge.
No Russians refer to them as "Krinkov", and there is a lot of speculation as to where that name came from.
BTW, just because a member has 12,000 posts doesn't mean he knows everything about all firearms. The AKS-74U is a rather specialized item and if you spend most of your time in the AR world you probably don't know much about them.