Change Tier 2 employer

HI

1-Can anyone elaborate, how long I should stick with my sponsor if I come to the UK on 3 years Tier 2 General VISA?
2-is it possible to change the Tier 2 sponsor without the knowledge of my Employer ( Existing Sponsor)
3- Can the salary in the RCos is different from the JOB offer?
4- Can my sponsor pay more salary than what is mentioned in Restricted COS? in this case do I have to seek any additional doc from the employer before apply for VISA.
5- if my employer promise to increase the salary after 6 months, should I demand him to mentioned in the Job offer?

Thanks in advance

1-Can anyone elaborate, how long I should stick with my sponsor if I come to the UK on 3 years Tier 2 General VISA?

There is no set time limit that you have to wait. Not sure why you believe there might be. To switch employers, you have to pay the visa and IHS fees again. You also don't even appear to be in the UK with a tier 2 visa yet!!

uk-tier-2-employer-sponsored-visas/pass ... l#p1838559

2-is it possible to change the Tier 2 sponsor without the knowledge of my Employer ( Existing Sponsor)

Your current employer is NOT involved in the processed at all.

3- Can the salary in the RCos is different from the JOB offer?

The RLMT and the CoS should match. If it does not, it creates heavy scrutiny by HO.

4- Can my sponsor pay more salary than what is mentioned in Restricted COS? in this case do I have to seek any additional doc from the employer before apply for VISA.

There are rules and processes your sponsor has to follow.

5- if my employer promise to increase the salary after 6 months, should I demand him to mentioned in the Job offer?

You cannot 'demand' stuff and an employer has no obligation to put anything like this in an offer letter. You will learn that by demanding stuff from UK employers could quickly get any offer of sponsorship/job withdrawn.