I don't understand why you did this "resetlog upgrade"
I would think this would break Data Guard.
I would consider recreating the Standby Database.
How I would have done it:
Disable log shipping from the Primary
Install 126.96.36.199 on Standby
Startup Standby in recovery mode do not run any upgrade SQL on the standby
Install 188.8.131.52 on Primary
Run upgrade SQL or DBUA on Primary
Re-enable log shipping
Monitor the redo apply from Primary to Standby --- this will also upgrade the Standby data dictionary
If you have flashback and the standby is ahead of the primary you might be able to flash it back.
select current_scn from v$database;
As you have opened the primary database in resetlog mode, then you have to re-create the standby database using the current backup of the primary database.
You should know that in 11g there reset log is on primary is not an issue.
redo logs will apply on standby.
We followed this step because we have migrated primary to new machine. old primary machine was not compatible for 184.108.40.206.0.
It is not required to recreate the standby only if FLASHBACK is enabled on both primary and standby database. Else according to my knowledge we need to re-create the standby database.
What does the Standby alert log say?
What is the next sequence of log it is expecting?
provide below output from primar yand standby: