Is it legal to sell our game outside the markeplace

Can I legally sell my game outside the epic marketplace? What agreements and conditions would still apply if so?

I think you are confusing about Epic Unreal Engine Marketplace where you can sell “game assets” and the different App Markets as Google Play,Steam,Apple Store,etc… As far as I know you can sell on all those app markets and just pay a share (5% I think) if you make more than 3000USD.

Right - there are no restrictions on where you can sell Products, as defined in the EULA. You just have to pay the royalty on gross revenue.

If I am remembering correctly, it is 3000 USD in gross revenue per quarter of the year. So the 3000 would reset every 3 months? Is this correct?

Yes, that’s correct