Explanation
Answer is CREATE TABLE transactions (id int, desc string) USING DELTA LOCATION
'/mnt/delta/transactions'
Anytime a table is created using Location it is considered an external table, below is the current syntax.
Syntax
CREATE TABLE table_name ( column column_data_type...) USING format LOCATION "dbfs:/"

Explanation
The answer is COPY INTO did not detect new files after the last load,
COPY INTO keeps track of files that were successfully loaded into the table, the next time when the COPY INTO runs it skips them.
FYI, you can change this behavior by using COPY_OPTIONS 'force'= 'true', when this option is enabled all files in the path/pattern are loaded.
1.COPY INTO table_identifier
2. FROM [ file_location | (SELECT identifier_list FROM file_location) ]
3. FILEFORMAT = data_source
4. [FILES = [file_name, ... | PATTERN = 'regex_pattern']
5. [FORMAT_OPTIONS ('data_source_reader_option' = 'value', ...)]
6. [COPY_OPTIONS 'force' = ('false'|'true')]

Explanation
The answer is, The Job cluster is best suited for this purpose.
Since you don't need to interact with the notebook during the execution especially when it's a scheduled job, job cluster makes sense. Using an all-purpose cluster can be twice as expensive as a job cluster.
FYI,
When you run a job scheduler with option of creating a new cluster when the job is complete it terminates the cluster. You cannot restart a job cluster.

Explanation
The answer is, Modify the task, to include time out to kill the job if it runs more than 15 mins.
https://docs.microsoft.com/en-us/azure/databricks/data-engineering/jobs/jobs#timeout