Hi,
These are the basic rules of naturalisation :

"Eligibility
To become a British Citizen an applicant must meet various criteria. The criteria differ depending on the individual circumstances of the British naturalisation applicant, however eligibility is usually based on the applicant having been in the UK for at least three or five years.

A British naturalisation applicant who has been in the UK for five or more years must:

Have held Indefinite Leave to Remain (ILR) for 12 months or more;
Have not spent more than 450 days outside the UK in the last five years and no more than 90 days should have been taken in the last 12 months;
Be over 18 years of age when making the application;
Be of sound mind;
Intend to continue to live in the UK if they become naturalised;
Be able to speak an adequate level of English (or Welsh or Gaelic);
Be of good character.

A British naturalisation applicant who has been in the UK for three or more years must:

Have held Indefinite Leave to Remain (ILR) and be married to a British Citizen;
Have not spent more than 270 days outside the UK in the last three years and no more than 90 days should have been taken in the last 12 months.
Be over 18 years of age when making the application;
Be of sound mind;
Intend to continue to live in the UK if they become naturalised;
Be able to speak an adequate level of English (or Welsh or Gaelic);
Be of good character".


This would answer your second question.

"The length of the work permit you obtain will depend on a number of factors which are normally more related to your employer and your job/project than the strength of your own candidature. Our general advice is that you should not worry if you get only a short term permit as it will normally be possible for it to be extended if you are still needed by your employer (and if you are not needed by your employer, you may well be able to find a new UK employer who can get another permit for you to stay in the UK).

After 48 months physically in the UK on a work permit, you will usually be able to obtain permanent residence. For this reason, it used to be the case that work permits were not issued for longer than 4 years. However as many work permit holders need to travel a lot, permits are now issued for up to 5 years, at the end of which time most people should have spent the required 48 months in the UK and be able to get permanent residence."

Triple H