As a Virginia attorney who has helped a great number of clients in Juvenile Court in Northern Virginia, the likelihood of the Juvenile Domestic and Relations Court judge issuing a bench warrant is pretty high. What that means is that you can be arrested at any time, on the street or at home, and taken to the Adult Detention Center (ADC). There you will appear before a magistrate who may set a bond, but as you have missed two court appearances, the bond may be high or he may deny bond. If he denies bond, you will then sit at the jail until the next day the court house is open, where you will appear before a judge who may choose to keep you in jail until your next court date or the judge may permit you to be released on bond.
My suggestion is to speak to the attorney that represented you at the initial hearing at the Juvenile Court. If you did not have a lawyer at the time, talk to one now --before you are arrested. The lawyer may recommend that you turn yourself in. He may also ask the court to remove the bench warrant if you agree to appear at the next court date.
If you don't want to spend extra time in jail, the best solution is to talk to an attorney, arrange to turn yourself in, if there is a warrant, and get the name of a bail bondsman that you can call in the event you are arrested and a bond is set.
The other issue is that the Juvenile Court judge, once you finally appear at a new court date, will impose some kind of punishment for your failure to comply with the terms of probation. Unfortunately, now that you are an adult, any jail sentence will be served in the ADC.
Even one failure to appear could result in a warrant against you, and new criminal charges. Here, you have two failures to appear. You also failed to do the community service and the drug class. This is reasonably likely to upset the judge. Since you apparently broke your promises to him you made the last time, why should the judge believe your promises this time? The best action is to get good local representation, and arrange to turn yourself in. The action of turning yourself in is very helpful, showing your willingness to submit to the system. The alternative, running for the rest of your life and hoping never to get caught, is unrealistic. The sooner you clean this up, the better off you will be.