The answer is yes. The employer can only offer an FSA if a group health plan is also offered, but employees who waive the group health coverage can participate in the Flexible Spending Account.
The answer is no. An HRA can only be offered if it is integrated with other group health coverage, and employees can only participate if they’re actually enrolled in that other coverage. (This answer is a little different for QSEHRAs and the new 2020 HRAs for individual coverage.)