Hi! I'm not sure if my visa is valid, and all "immigration consultants" can not answer me directly. My short-term entry visa is attached to my Certificate of Sponsorship, which has been revoked together with the contract. Be default I assume that my visa is revoked too, because I don't want to take that chance.

That's fair.

Assuming this is a T2 Skilled worker visa, working for an approved employer that sponsored the visa application is one of the conditions of this visa type. Very similar to H1B.

It's definitely possible to thrive here but moving somewhere with a _much_ higher cost of living without having a job is a bold move.

And, to be frank (if sympathetic), I'm not sure unemployed Russian wanting to move to London has the strongest hand to play right now, even if the software developer job market is still reasonably strong.

for a software engineer, i think the risk is close to 0 :)

That's a big assumption to make.

UK work visas are linked to the specific employer so they become invalid if the offer is withdrawn.

A sponsored Skilled Worker Visa becomes invalid 60 days after employment ends.

In this case the employment never even started. The 60 days is for people already in the country to either move out or find another visa sponsor.

Only 60 days? Wow. Given how long the interview process can be for some skilled positions (as evidenced by the author's lengthy hiring process), I'm surprised this window for finding a replacement job is so short.

A rule of thumb for dealing with the Home Office is that nothing is done out of kindness or common sense (or even legality). Everything is done with the aim of removing from or denying entry to as many people as possible. And even at this "job" it is mostly ineffective.