Misc: In 1917 Provisional government of ---------- established, Republic proclaimed. ?

Questions

in Arthurian legend who found the Holy Grail?

British Scientist Sir Charles Wheatstone is said to be the inventor of the concertina and which other instrument?

What was built along the south coast to guard against French invasion?

Where is Britains tallest nave?

Who did a series of paintings of young men and light reflecting on water?