Welcome to the board, Polly.
(Please capitalise I every time you use it.)
1.These are all correct.There's nothing interesting on TV.
There's nothing interesting on the TV.
I'm watching a comedy show on TV.
I'm watching a comedy show on the TV.
2. A series is a number of programmes featuring the same characters week by week, but telling a separate story each time. There may be a continuing thread running through - such as a delevoping love affair - but it is not necessary to follow every episode.
A serial has several episodes following on from each other telling one story over a number of weeks. If you miss an episode you may find it difficult to catch up later.
Student or Learner