So, assuming the visa side is OK you are going to:

See all of London in 1 day, Athens in 2 days, Istanbul in 1 day and Munich in 1 day - given that you have travel to/from airports, check-in, etc.

Let me ask you - do you think a European visitor would get any benefit at all from, say: KL in 1 day, Bangkok in 2 days, Jakarta in 1 day and Singapore in 1 day?

You then plan to do basically the same thing for Vienna, Switzerland (!), Barcelona, Porto and Stockholm.

It's something we see often on this forum - what looks to me like an over-ambitious itinerary that will leave you exhausted and with no time at all to have really seen or understood anything...

As a business traveller, I'm often in three or four countries during a week - trust me, the only memories are of airports!