Once again the 'Cat proves its versatility. This is the first time I've been able to answer every part of one of these Christmas quizzes.
In the past I've worked at it from late Nov to early Jan without complete success!

To give a further idea of just how complex this quiz can be, I'm including the 1998 version (for which I have the answers). Clearly some questions need to be deciphered before the answers can be sought.
Nigel

JAD's Christmas Quiz 1998
1.        What started at Melbourne and ended some 5,000 kilometres later at Suzuka?
2.        Connect Audrey Hepburn, Tintin, Waterloo, George Le Gloupier and septante-deux.
3.        Why won't the new £2 coin roll properly?
4.        Ground floor.., perfumery, stationery and leather goods, wigs and haberdashery, kitchenware and food. First floor... what?
5.        How were muscardirzus avellanarius and gryllotalpa gryllotalpa, or cypripedium calceolus and segmentina nitida, each equivalent to boletus satanas?
6.        Distinguish between...
          (a)        Alexandria and Siena.
          (b)        Becket and More.
          (c)        Canterbury and Hippo.
          (d)        Avila and Lisieux.
          (e)    Just and Great.
7.        Name the third Monday in February, the last Monday in May, the first Monday in September, the second Monday in October, and the fourth Thursday in November.
8.        Three threes... Bruichladdich, Fettercaim, Glencadam, Glenfiddich, Knockando, Lagavulin, Laphroaig, Lochside, ana Macallan.
9.        which is the odd one out, and why, amongst Ghost, Phantom, Wraith, Dawn, Cloud, Shadow, Spirit, Spur and Seraph?
10.        Explain how...
    (a)        An Italian divided by a Frenchman equals a German.
    (b)        A differentiated Mancunian is a Glaswegian or a Cantabrigian.
    (c)        273 Ulster-born Scotsmen equal 32 Polish-born Dutchmen.
11.        Norway nil points — but when, where, who and with what?
12.        Distinguish between the Lord Advocate, the Lord Justice-Clerk, the Lord Justice-General, the Lord Ordinary and the Lord President.
13.        How are Severn, Aust and Kingsgate one above Parson's Pleasure, Swanscombe, and Zoo West?
14.        Complete the sequence — arms, thistle, leek, flax, oak, arms, thistle, leek, flax, oak, arms, lion, dragon,
15.        Why might Scouts be particularly drawn to Aston Villa Football Club, Merchiston Castle School or the Metropolitan Borough of South Tyneside?
16.        Why did two lost children need fourteen angels?
17.        Place Brian Boru, Brother Cadfael, Geoffrey Chaucer, El Cid, Erik the Red, Lady Godiva, Bishop Hatto, Hereward the Wake, Robin Hood, Prester John, Genghis Khan, Omar Khayyam, Llywellyn ap Gruffydd, Macbeth, the Pied Piper, Marco Polo, William Tell, Good King Wenceslas, Dick Whittington and William the Conqueror in chronological order of their (real or supposed) deeds of fame. Supporting argument may be included if you wish.
18.        This year's cipher owes much to M. Mot-clé de Tableau, a sixteenth-century French cryptographer.
GPAZF SUTBZ ARHRL IVXJO IVYWP QGZWE UUOGL SBWLX WSQWE.
19.        For their winter expedition, the Venture Scouts are contemplating a five point hike in which they will visit (in any convenient order) the villages of Norton, Sutton, Easton, Weston and Middleton. Where in Great Britain is the shortest route meeting these requirements? (Any entrants who actually complete such a hike themselves may claim bonus marks.)
20.        Say it with flowers — Sir Percy Blakeney, Sheffield Park to Horsted Keynes, Sebastian's sister, Nobody's son, a New Year football game, a careless baby farmer, the fall of Caetano, the reign of Ahmed III, the Vicar of Wakefield, and the belle of Dogpatch USA.