Please indulge me.
1a. If a European monarch - say, the future King/Queen of Spain - wanted to be crowned by the Pope, assuming that he is willing and able to do it, can he do it?
1b. Would the coronation be held at the Vatican or in the monarch’s capital?
1c. Does being crowned by the Pope have any special statement or meaning? Does it change the monarch’s regnancy over his/her realm? Does it affect the relationship between the monarch and the Catholic Church or the realm and the Catholic Church?
1d. Would the Pope crown a non-European monarch who is Catholic and desires it?
2a. When the Pope is crowned, who places the crown on his head?
2b. What are the chances that a future Pope, if not the future Pope, will permit himself to be crowned rather than the current trend of only being inaugurated?
That’s all for now!
WRS
No one up for a little popery and crown speculation? 
WRS - We are not amused.
It’s customary for any Christian king to be crowned by a bishop, and in a Catholic country such as Spain the bishop would be a Catholic one. Coronation by the pope – the bishop of Rome – might have symbolic political significance, WRT to Spain’s relationship to the Church, but it wouldn’t be any different legally. The only European monarch who traditionally was crowned by the pope was the Holy Roman Emperor – and that practice was discontinued in 1508. http://en.wikipedia.org/wiki/Holy_Roman_Emperor (Pius VII officiated at Napoleon’s coronation as Emperor of the French, but Nappy made a point of putting on his own crown.)
For that matter, the popes themselves are no longer installed in the traditional papal coronation ceremony, with the papal tiara . The practice was discontinued by John Paul I. http://en.wikipedia.org/wiki/John_Paul_I