Tier 2 general Visa extension

Hi,

My COS says that RLMT is not met. When i asked to my employer, they are saying that RLMT is not required in my case since my role is under the skills shortage list and SOC is 2136 Programmers and software development professionals
1)What would be the process for extension of this visa after 3 years.?
2) would there be any problem or eligibility criteria for extending the same visa.(shortage occupation)?
3) Would i need a new COS required with RLMT done?
4) would SOC 2136 should be in skills shortage list at that time for visa extension?

Any help would be greatly appreciated.

Thanks

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