If talking about testing, then pattern and free dance are not inter-dependent. You need to pass tests in each stream in order, but you can do as many or as few of the others as you wish, as with any of the NISA test streams. Also, no-one does variation dance any more, just pattern and/or free dance, plus field moves which is for everyone, dance or free.
Most dance skaters do FM and CD at first, adding FD later, when starting out.
As an informal statement, describing yourself as being "level 1 dance" would imply that you had passes in all of level 1 CD, FD and field moves, whilst "level 1 free" would imply you'd passed all of level 1 elements, free & field moves. These are just informal phrases, and a shorthand to describe your test level, with no official basis.
For solo dance series competitions there is a test level for each category. This was until previously just being taken on CD level, but an equivalent field moves level is now being enforced more strictly. Point of order on the previous comment - level 4 is juvenile, with level 6 being basic novice. If you were to enter an open, you'd enter CD & FD at the same level, going on your CD level.
There is also an age cut-off for each of the "named" solo series open competitions, for qualification for the British champs. You can still enter when over-age at the opens, but cannot qualify for the British at that level if over the age limit for the level. These start at level 4/juvenile.