No a 4 month old beardie is not considered grown. At 4 months he would be considered a Juvie. And as long as the hopper is not bigger than the dragons head length wise and main body of the hopper is comparable to the space between your dragon's eyes then you are fine.
hard to tell from the pictures. you really should just measure the space between your dragon's eyes and make sure that it is bigger than the length of the locusts.
but locust are quite skinny and their chitin(apart from the legs) seem quite soft so i thought that the "space between the eyes measurement" doesn't matter for locust.
I just set Swordtail's timer for his bath and paused it so I could actually fill his soaking bowl up and he crawled over my phone and canceled the timer
Mirage came out of brumation on April 26. He was doing great. On May 2 he started acting funny. We just redid his tank, and he keeps going into one of his hides. He just lays there. He shows no intrest in food. HELP!