He/she is probably around 4 months or so now. I’m guessing that because he looks about 8 weeks-ish in the first picture. If he is a boy, his jewels should be visible at this point. So take a look! If they are there, they will be located above/in front of his genitals area. They look like 2 thumb pads peeking through the fur. If they are there, then there is no mistaking it’s a boy. If they are not there, then that doesn’t guarantee you have a girl. LOL
He/she is adorable by the way!
You can start introducing veggies now. Just make sure to try different kinds one at a time to make sure nothing upsets his stomach.
It’s always a good idea to take a new bunny (or any pet) to the vet just to make sure everything is good. It’s a good idea to get yourself established with a vet before there is a problem and to make sure they are rabbit savvy. You can discuss neutering/spaying as well and your vet will should be able to tell gender at this age.