Does the record company have to release the records I make?

It depends if you have a guaranteed release commitment in the contract. Most record deals have a guarantee to release at least one record.

However, if they are not completely convinced of its viability, they are unlikely to want to spend money putting out a record which in their opinion has no chance of success. In this case, they may elect not to accept the master recordings. 

Will the record company want worldwide rights?

In most cases, yes. Major labels and many independents will want the rights for the world.  This situation changes when you sign to a smaller independent without an international track record or when you are an act that is already established. If this was the case, you might give UK rights only. (The record companies make money by signing your rights for the world, then licensing the copyright to different territories such as Germany, Japan and the USA)

Should I sign for one album or more?

Do not be fooled into thinking a six album deal is better that a one album deal. If the first release flops or does not make money for the company they will have the option to not record the subsequent five.

If I get dropped by a label, is my career over?

Not at all. Many recording artists are dropped by one label only to be picked up by another and go on to great success. There are many factors involved when an artist is dropped from a label. One of the most common reasons is that a key member of staff leaves the record company and the band no longer has its advocate within the organisation.