No need for a visa, as the UK is a participant in the Visa Waiver Program.
Yes
NO, in most cases you do not need a visa to come to the UK for a short visit
yes
No UK citizens do not need a visa to go to Singapore just like Singaporeans do not need a visa to enter UK
its natural u ned visa to travel from one country to another
no
Yes
No, Serbian citizens doesn't need visa for Schengen countries, but they need visa for UK and Ireland.
No - you still need a visa to enter the UK !
Yes they do.
Yes