I don't see this as too much of an issue given your past experience and tenure. You have learnt a valuble lesson though - don't join a company just because you like the sound of one project! Projects can change. Concentrate on finding a job that you like a range of work and the type of projects they do.
Whether there is anything else i can do? - You sound like you've made up your mind, but have you tried seeing if there are any other interesting projects?
How do i manage this in the conversation with the next recruiter/company? - You tried it for 3 months and decided it wasn't for you, just tell them the company wasn't a good fit. As I said, given your tenure at previous places it shouldn't be an issue
- Whether there is anything else i can do?
2a) When Do i tell them at that I am working for this company for very short term, and elaborate the problem? Do i tell the recruiter? or do i tell only to the company? - You sound like you've made up your mind, but have you tried seeing if there are any other interesting projects?
- How do i manage this in the conversation with the next recruiter/company?
- You tried it for 3 months and decided it wasn't for you, just tell them the company wasn't a good fit. As I said, given your tenure at previous places it shouldn't be an issue
2a) When Do i tell them at that I am working for this company for very short term, and elaborate the problem? Do i tell the recruiter? or do i tell only to the company?
- Don't, just let them bring it up if they have an issue. They will see it on your CV anyway
Number 3 didn't seem to contain a question but if you want to become an entrepreneur I would say go for it and good luck! (Note that's my opinion only)