Where to find schema.xml file for solr 5, or it's should be created manually, Should I create schema.xml for each core or schema.xml for each example?
In cloud mode, you'll have a schema per collection. This schema will not be added automatically. You need not create the file yourself from scratch. You can find a ready to use configset in the example directory that you can then modify for your own use.
In cloud mode, all your config files are stored on the zookeeper. You can connect to it using the zkcli.sh script provided with the solr installation. For 6.x you can find it under ${SOLR_HOME}/server/scripts/cloud-scripts/zkcli.sh
To upload a schema set:
server/scripts/cloud-scripts/zkcli.sh -z localhost:9983 -cmd upconfig -confdir example/files/conf -confname collection1
Create a new collection and then to retrieve files:
server/scripts/cloud-scripts/zkcli.sh -zkhost localhost:9983 -cmd get /configs/<your_collection_name>/managed-schema