Development wanted to do some changes in the dev database, which needs to be rolled back once testing is over.
So we have chosen to create flashback restore point before they do the changes and flashback the database, once testing is over.
Now there is a little twist. This is a data guard environment, i.e it has a standby database. Doing flashback on the primary database will break redo apply.
Below are the steps to flashback primary database in data guard environment safely.

1. Make sure both primary and standby database have flashback enabled.

2. Create a restore point in the primary:[PRIMARY]

Now we can confirm the dev team to do the changes in the primary database. And once dev team confirmed that their testing is over,
Follow below steps to flashback primary.

4. Shutdown Primary database [ PRIMARY]

5. Mount primary database [ PRIMARY]

6. Flashback primary database [ PRIMARY]

7 . Open primary database in resetlogs: [ PRIMARY]

8. Cancel the recovery on standby: [ STANDBY]

9. Flashback standby database [ STANDBY]
Get the SCN value from point 2 (the respective scn of the guarantee restore point)

10. Start recovery [ STANDBY]

NOTE:
If you are getting below error in standby, then we need to recreate the control file in standby

Sequence 22 does not yet exist in new incarnation, and it has been already
applied in the old.

SEE – How to recreate standby controlfile