What if I want to travel to Spain and England at the same time?

Need to apply for Schengen visa+UK visa.

Britain is not a Schengen country, and its visas are separate, with multiple round trips within six months.

Schengen visa is 90 days at most. It depends on the number of days you apply.

After getting a visa, generally speaking, you can enter the country with a round-trip air ticket to travel itinerary and local hotel orders (if you stay in a hotel). If there is only one-way ticket, it will be in trouble.