Is it necessary to have a separate voting tag for each rating when using Fivestar? By design I will have a ratings page with many things to rate - 30 different Fivestar ratings altogether in the same content type.

Is it necessary to have a separate voting tag for each of these 30 ratings? Because I see there is a character limit on the field in Fivestar tags configuration and I can't input all my voting tags.
Yes, you need a separate voting tag for each ratings in the same content type, if you use the same for multiple fields, each field will recieve the same rating.

You can make a test, create two fields with the same tag, go to create one node and rate one field, refresh the page and you will see the same rate in the other field.