Hi! My DS just finished his first competitive season as a level 4. He's now training for level 5.
He turned 10 in February, but there were level 4 kids as young as about 6. At meets, the boys are grouped by age, but the ages vary, so sometimes, there might be a 10 and up group whereas at another meet, there's an 8 and up group. The younger ages also vary. I think the groupings depend on how many kids are in each meet. So a big meet might have a 7 year old group whereas a smaller meet might combine the 7 and unders together. I hope I'm making sense!
The boys complete alongside but not against kids of other ages. So you might have a 7 year old do his routine and then a 10 year old do his routine, but the rankings are separated by age. Again, though, those age groups vary depending on the meet. All the boys in level 4 will do the exact same routine, though, regardless of their age. They have required moves and optional (or bonus) moves which give them extra points.
Recognition varies as well. I think at all of our meets, all the boys were recognized in some manner, but the particulars vary. My DS got ribbons, medals, and trophies for participating. Then there are prizes for placing well in the age group, but these prizes vary. And, some meets do the prizes for the top 10, others for the top 5. It just depends.
The season runs from December until March. In our region, level 4s can go to the state meet, but that's as far as they go (and they ALL get to go if they've been competing in qualifying meets during the season). Higher competitive levels can then move on to regional meets which include the best gymnasts from the various states, but a level 4 does not have that opportunity.
Be prepared to travel a bit too. We often drove an hour or more to meets and stayed overnight once because the meet was two hours away, and we had to be there really early in the morning. The meets are almost always on weekends, but the times vary. You can plan on spending half a day or so at each meet, or about 3-4 hours at each one.
Also, at least around here, once the boy starts the season in an age bracket or a level, he does not move up. So my DS was 9 when he started and then turned 10 before it was over, but he stayed grouped as a 9 year old in the meets. I've been told the girls are different in this way, but I'm not sure.
Have fun! Competitive gymnastics has been both emotionally and physically tough on my little guy (he was crying tonight after practice because he got upset at his coach), but it's good too.