Q1. The whole purpose of this visa is to establish or set up a business. It is not a visa that you can simply come to the UK and do nothing about setting up a business or subsidiary and do any work you wish to for any employer.
https://www.gov.uk/representative-overseas-business
You can apply to come to the UK as a representative of an overseas business if you’re from outside the European Economic Area (EEA) and Switzerland and you’re either:
the sole representative of an overseas business planning to set up either a UK branch or wholly owned subsidiary
an employee of an overseas newspaper, news agency or broadcasting organisation posted on a long-term assignment to the UK
Q2. No, you cannot work for any other business. This is very clearly stated on the UKVI website. This visa is NOT a general work permit where you can work for any employer. There is no such UK visa anymore.
https://www.gov.uk/representative-overseas-business
What you can and cannot do
You can:
work for your employer, full time
bring your family (‘dependants’) with you to the UK
apply to extend your visa
apply to settle in the UK after you’ve been here for 5 years
You cannot:
work for yourself or any other business
stay in the UK if the sole representative arrangement is ended by your employer
switch to this visa from any other visa category
get public funds
Q3. If you meet the requirements of the visa and residence, there is no reason you won't qualify for ILR.
Q4. Members are NOT permitted to post the names and details of advisors on the forum. You or your employer will need to find one yourselves.