No. It is a major illness that can disrupt relationships vocations academic work financial security etc. It may lead to jail or suicide mania usually produces irritability which isn't fun--i don't see it as being "best".
Terrible "lows" First of all, the "highs" of mania are more a story about an abundance of boundless super-charged energy (often associated with grandiosity and sometimes paranoia) and not so much a story about happiness and joy. Secondly, the "lows" can be very low and accompanied by suicidal despair.
Best? Most fun? Most interesting? Most difficult? It is hard to know what you mean. For those with severe mental illnesses, most don't find a lot of good to having the disorders that they have. Most would choose to have no illness, mental or physical. Manics get themselves in lots of trouble and can ruin their lives and the lives of those around them, especially in the most severe of cases.
Any is hard. It is hard to live with anyone suffering from a mental illness. If you are in distress make sure to get some help support and treatment for yourself as well.
No, it depends. What you may be dealing with may be very difficult for you. Have you heard of the national alliance for the mentally ill or nami? There may be a branch in your area and you could check. Nami is a support group for families of those with mental illnesses. It can be extremely tiring and frustrating trying to deal with someone who has a severe mental illness. I've used Risperdal consta with success.
Yes. Historically, schizophrenia and bipolar disorder have both been known as "severe mental illnesses". This wording can be important as receiving help from mental health centers sometimes is predicated upon meeting the definition of "severe mental illness". You used the word serious and bipolar disorder meets that definition too. The risk for suicide or homicide is what makes it so serious.
How do you mean it? I suppose the folks handling decisions are the best ones to ask, but I really can't imagine how severe bipolar disorder would not qualify as a disability - at least partial. However, many bi-polar people do work even though it is difficult. But, if you mean: can I hold an employer to blame for being diagnosed as bi-polar, probably not.
No, but.... ..Bipolar is itself serious. If not properly treated, bipolar in its later stages cause severe deterioration in relationships and career. It then also has the highest risk of completed suicide of any mental condition. There exist combination diagnoses as well, in which another serious condition co-exists, but this is not really the change of one into another. Professional care is urgent regradless.