No. It is bigamy and it is a crime in the United Kingdom.
Yes, this is legal in the UK.
Yes, if you are a citizen of UK.
One - and only one. Poligamy is illegal in the UK.
In the UK it is legal for cousins to marry, so it is certainly legal for cousins to have children. King Henry VIII changed the marriage laws on that point so that he could legally marry his cousin.
Assuming that you have a legal heterosexual marriage in the UK (that has government certification), that marriage will be recognized in Algeria. As a result, in order to marry an Algerian, you will need to get a divorce. If you have a same-sex marriage in the UK, you will not need to get a divorce in the UK to marry the Muslim in Algeria, but that marriage will not be recognized in the UK (because you would now be married to two people contemporaneously). If you are not married in the UK, then, obviously, you will not need a divorce to get married.
I suggest you don't because you may get in trouble with your partner in the UK
it is 65 at the momment
In the UK, yes.
It is legal to marry your first cousin, once removed in the UK. Cousin marriage has been legal since King Henry VIII decreed it so. However, there's currently talk from government officials about banning the practice.
Very bad idea. Makes children with health problems.
Yes. Same-sex marriage is legal in both the UK (except for Northern Ireland) and Spain, as well as several member states of the European Union. In countries where it has been legalized, same-sex marriage is legal for all purposes, including for immigration.
Yes, beginning March 29, 2014, they can marry in England and Wales, but not in Scotland or Northern Ireland.