The 4Ever is a fantastic seat. It's a 4-in-1 seat that can be used from birth to age 10+. It has a high harness height that allows it to fit kids well rear facing until their shoulders are above the lowest belt slot and in booster mode until they are too tall for it to work safely. It has a premium UAS and top tether anchor system that looks more like a stapler with red buttons to release it (it cannot be installed using either of the vehicle seat belts). The headrest/harness height adjustment is super easy to make. It's a smooth, no rethread system that only needs a quick push to move it.
The seat also features a built-in head support pillow and body insert to aid in fitting newborns and small infants. It is a very nice feature to have since most smaller infants will need this extra support to ensure their shoulders are below the lower belt slots. The seat also has a pair of cup holders which was nice.
To convert the seat to a booster, first you will need to remove the harness. There will be an external adjuster handle and a harness release button in the middle of the seat. After removing the harness, you will need to remove the lower anchors from the vehicle and find where the shoulder strap connects with the seat. The seat has red covered belt guides for the lap and shoulder belts in booster mode.