A CWOF is similar to a plea of "nolo contendre." That is, it requires an admission that the state of Massachussets would have enough evidence to convict you of some or all of what you were alleged to have done. There is, thereafter, a probationary period after which the matter is ended without a finding of either guilt or innocence (essentially, a suspended sentence
Although you would have the legal right to say that you have never been convicted of a crime, these are not sealed and can turn up on your record and on CORI where, depending on the level of the background check, they can appear.
From what I have read, under MGL Chapter 276, Section 100A, a defendant will be able to seal his misdemeanor
after 10 years or his felony after 15 by petitioning the Commissioner of Probation, if there are no other offenses other than traffic matters where the fine doesn't exceed $50. Sealing should make the matter invisible to most employers (government agencies and some licensing divisions, however, can see what most everyone else is not allowed to access).
There's a shorter route to a sealing, (that is, without waiting 10 or 15 years) although it is discretionary, so the outcome would be less certain. That would be to petition the judge directly under MGL Chapter 276, Section 100C, asking for a sealing in the interest of justice
. If the judge decides that the state has less of an interest in keeping the record open than in grantic your request, he can do that for you. You would show a compelling governmental interest that would outweigh keeping your CWOF unsealed, and that would best be done via a lawyer.
As to the rest of your question, see this
for your rights as an applicant for hire.