The final regulations in this area simply changed one element of the definition of QNECs and QMACs. Old definition...QNECs and QMACs had to be 100% vested when contributed. New definition...QNECs and QMACs have to be 100% vested when allocated. It is this change that now allows forfeitures (which, by definition, were not 100% vested when contributed) to be used to offset QNECs and QMACs.
So, the answer to your first question is "Yes". Any QNEC, including those necessary to correct certain operational errors under EPCRS, can be offset by forfeitures.
Regarding your second question I am going to assume that you are referring to the employer match that an employer must make when a participant has a lost deferral opportunity in a plan that provides for an employer match. Per the EPCRS (Rev. Proc. 2019-19) APPENDIX A section .05, these matching contributions are also made in the form of a QNEC not a QMAC. APPENDIX A section .05 also makes it clear that correcting for a missed deferral opportunity (deferral and match) occurs after other qualification requirements are met (i.e. ADP/ACP tests) and that the ADP/ACP tests may "disregard the employees who were improperly excluded."
So, the answer to your second question is 1) the QNECs necessary to correct a missed deferral opportunity and the associated match are not included in either the ADP or ACP test, 2) since the corrective contributions have to be made as QNECs they must be 100% vested and cannot be subject to a vesting schedule and 3) the earnings are part of the QNECs and, therefore, the employer can use forfeitures to offset them.
Michael Hatlee, QPA, QPFC