Any negotiator experience this kind of situation? Tenant not allow the new purchaser to do final inspection before sign sales & purchase agreement. Do the new purchaser has the right to do so with current owner permission? Thanks. 

Yes, tenant saying that owner selling property not even his issue or responsibility to entertain. He feel being interrupt and the tenancy still got 6 months only expired. So what we suggest the tenant is to terminate the contract with mutual agreement between both parties. Owner agreed with that and tenant as well. Since it will create more problems for the new purchaser in the future if the tenant not so cooperative.

same rice feed all kinds of people... we get to see all sorts of behaviours

If mutual agreement can be achieved then case can be considered closed. 

Yes. At least everyone satisfy for the outcome. New purchaser able to find new tenant and rent it out with higher rental; current owner no further headache and proceed with the S&P signing; while current tenant able to find better deal which he already got some condo in mind and ask us to search it for him. Happy Ending :) Thanks for all the recommendations.