Can I use the LATCH anchors that are not designated for the vehicle seating position I have selected for the Foonf convertible car seat?

No. LATCH anchors have a required standard spacing of 11 in. (280 mm) from center point to center point. In Rear-Facing, using the Rear-Facing LATCH Belt to connect to lower anchors that are closer together or farther apart than 11 inches will not allow for a secure installation. In Forward-Facing, Foonf is designed with a Rigid-LATCH system and will only be able to connect to lower anchors designated for that vehicle seating position.