No, it is not possible to have a sensor with a higher software version than the manager.
You will need to upgrade the manager first, then you can upgrade the sensors.
You should review the Installation guide to find out if you can upgrade from 184.108.40.206 directly to 8.2.x software, and if your current servers meet the requirements to run 8.2.
There are changes to the database structure when moving for v7 to v8 and if you have a large database it can take a long time to convert it.
If you do not need to keep your existing alerts in the manager you could just setup a new 8.2 manager and move the sensors to it one at a time and upgrade their software.
Good luck with your upgrade.
Thanks peter.mason that is what I thought. I will try first the upgrade to 8.2 (supposedly it can be done and I have tested it on lab), if something goes wrong a new manager is the next step.
Thanks and regards.