Can a adult charged with a felony as a juvenile own a firearm in the state of Texas?

Yes, so long as the probation is completed. One of the ways you are disqualified from possessing firearms is if you are a convicted felony. However, a juvenile adjudication for a felony offense is not a felony conviction. Similarly, if a juvenile charged with a felony received deferred adjudication, and the case is now dismissed and probation is completed, he should be eligible to possess a firearm. Seek the services of an attorney prior to buying a firearm, however, to ensure your particular case is good.

Yes, so long as the probation is completed. Do not assume your records are sealed, Your juvenile record is not automatically sealed, You may need to retain a lawyer to see if you can seal your record,