Use Stereo Integrated AMP as a Mono Block

Not really, it is still a stereo amp, but you will now have bi-amped your center channel. :)

but both L and R to my Integrated amp will recive the same signal to amplify so why not I use the L and R out of the Integrated to biwire my Center channel

Mono blocks benefit from physical separation and separate power supplies, which you won't have with this arrangement.

That’ll work, but you might need to set a “reference” volume level on the Exposure (I used to use 12:00 as it’s consistent and easily repeatable) when you set the individual speaker volume levels with the Denon unless the Exposure’s A/V input acts like an HT bypass and puts it into unity gain, then you don’t have to worry about the volume control because it’s out of the picture.

As a follow-up question, is this strictly a HT system or is it also for 2-channel listening? Just asking because there may be another more preferable hookup option here.

Thank you for the inputs, yes its only for HT setup. And I dont have the control on the volume on my exposure when I connect as AV. But I do have the Denon volume level to setup individually for the center.

I have Exposure 3510 Integrated amp.

It has the HT ByPASS as you said. Thank you soix.

Great.  Enjoy!