Is it possibel to do migration from 7.5 to latest version of CUCM?
Yes, via PCD migration
Should i upgrade it to 10.5 Verison only?
That's up to you, *ideally* you should be in the latest available release per the best practices
If, I will go with higher version, then what would be behvaour with other location?
As you do not provide any explanation of what is configured between locations and CUCMs, there is no way anyone can answer this, only YOU who has the knowledge of your deployment should know the answer
Very Imp, How should i restore the backup of old one and also what precaution need to be taken?
DRS can only be restored on the EXACT SAME release from which it was taken, but this does not matter at all for a PCD migration as the original cluster can remain active.
If you're not familiar with any of this, I'd strongly suggest you reach out to a Cisco partner or reputable consultant for assistance with this migration.
if this helps, please rate