imac monitor help

Yes..

Built-in Display:21.5" 16:9 WidescreenNative Resolution:1920x1080

Details:This model has a 21.5" LED-backlit 16:9 widescreen TFT active matrix display with IPS technology and a native resolution of 1920x1080. The cover glass is fully laminated to the LCD and it has anti-reflective coating to reduce glare. Apple does not report viewing angle or contrast ratio.

2nd Display Support:Dual/Mirroring* 2nd Max. Resolution:4096x2304

Details:*This model can simultaneously support the internal display at full native resolution and up to 4096x2304 on an external display in both extended desktop (second workspace) and video mirroring (internal display duplicated on the external display) modes.

Video (Monitor): 2 (Thunderbolt 2)

Details:This model is equipped with two Thunderbolt 2 ports. Thunderbolt 2 is backwards-compatible with Mini DisplayPort-equipped displays as well as adapters that are compatible with Mini DisplayPort (DVI, VGA, dual-link DVI and HDMI). It also can support other peripherals that use the Thunderbolt 2 standard.

https://everymac.com/systems/apple/imac/specs/imac-core-i5-2.8-21-inch-aluminum-late-2015-specs.html#macspecs2

Oh, looks like not...

Video Card:Iris Pro 5200VRAM Type:Integrated

Details:This model has an Intel Iris Pro 5200 graphics processor that shares memory with the system.

Which "Tapered Edge" iMac have video processors with dedicated memory? Which have integrated memory?

Standard VRAM:1.5 GB* Maximum VRAM:1.5 GB*

Built-in Display:21.5" 16:9 WidescreenNative Resolution:1920x1080

Details:This model has a 21.5" LED-backlit 16:9 widescreen TFT active matrix display with IPS technology and a native resolution of 1920x1080. Apple also reports that the "cover glass is fully laminated to the LCD and an anti-reflective coating is applied." The company does not report viewing angle or contrast ratio.

2nd Display Support:Dual/Mirroring*2nd Max. Resolution:2560x1600 (x2)

Details:*This model can simultaneously support two external displays up to 2560x1600 via Thunderbolt.

This model is equipped with two Thunderbolt ports. Thunderbolt is backwards-compatible with Mini DisplayPort-equipped displays as well as adapters that are compatible with Mini DisplayPort (DVI, VGA, dual-link DVI and HDMI). It also can support other peripherals that use the Thunderbolt standard, which provides a maximum theoretical 10 Gbps of bandwidth in both directions.

https://everymac.com/systems/apple/imac/specs/imac-core-i5-2.7-21-inch-aluminum-late-2013-specs.html#macspecs2

Any Luck yet?

I think it will.