I have a conviction for causing serious injury by dangerous driving from 2018. What i would like to know is how long dvla will have this information for. Ive read online that its only held on the database from 4 years after the date of conviction? Is this true? I did a license check online and it didn’t show this information. Will I still be able to get my provisional license? If I do not declare this on the D2 form how would they find out without contacting the police records.
A dangerous driving endorsement stays on your licence for 4 years but that does not mean the conviction is wiped off your DVLA record after 4 years, I’ve no idea what convictions the provisional licence form asks for but I would strongly recommend that you complete the form honestly.
I doubt that the conviction will stop you getting a provisional licence or full HGV entitlement after passing the test, but lying on the application form could come to bite you badly 
My advice would be to declare it, for me personally if I didn’t declare it, these things have a habit of being bitten on the @ss at a later date.
I’m not sure how it works when a conviction ends when it’s wiped off the DVLA records so how would this affect obtaining insurance, would someone have to declare that conviction that’s ended, even though it’s still lurking around somewhere on a database,and if they didn’t declare it and there was a claim, would that mean the insurance would invalidate the claim and cancel the policy?
Four years from date of conviction, but also depends what the conviction consisted of. Often includes having to pass test again, which is why your applying for provisional and then to pass an “advanced” test compared to the normal driving test.
Some insurers and employers ask for a longer period for insurance purposes, if so then consider carefully how you answer, they will usually refer why they want more than the rehabilitation of offenders period.
Did you have to attend a TC driver conduct hearing re your HGV?
Best option is get legal advise for your circs so you know when to notify or decline to reply
A conviction for dangerous driving is always an extended driving test, that offence is two years custody then have to retake the driving test to get the licence back again.