The Gorsedd Circle

I wonder, can the guardians of Welshness (is exactly how I see you) help me in these, my enquiries here?;

1.the Gorsedd ( Throne ) Circle in front of the National Museum & Art Gallery in Cardiff was erected in 1899, that's right isn't it?

2.the Gorsedd Circle standing in the nearby Coopers Field, slightly to the west of today's Cardiff Castle was erected in what year, please?

3.in 1908 (?) the Welsh National Eisteddfod's Maes was the Royal Albert Hall -I believe, consequently where did the organisers put the Gorsedd Circle for that year's event, please?

& 4.when was the last and final stone 'henge' [ i.e. long-lasting and definitely of stone ] erected to commemorate the selection main event site of an Eisteddfod? -I mean, where is it to be seen? And in what year was it constructed, please?

If you'd answer the above questions, then I would be most obliged to you all.

Many, Many Thanks, Gerry Lyons, Cardiff, Wales.