Short answers, pulled from the story.
The Matilda II's armour was the heaviest of its era, with the front glacis reaching 78 mm and the cast turret 75 mm all round. German anti-tank guns could not penetrate it at normal combat ranges, and only the 88 mm anti-aircraft gun, repurposed as a ground weapon, proved a reliable counter.
A total of 2,987 Matilda IIs were produced by Vulcan Foundry, John Fowler and Co. of Leeds, Ruston and Hornsby, the London Midland and Scottish Railway at Horwich Works, Harland and Wolff, and the North British Locomotive Company in Glasgow. Peak production of 1,330 was reached in 1942, and the last tanks were delivered in August 1943.
The Matilda II was phased out from late 1941 in favour of the Infantry Tank Mk III Valentine, which carried similar armour and armament on a lighter, faster, and cheaper chassis. The Matilda's twin-engine arrangement was complicated to maintain, its top speed averaged just 6 mph in desert terrain, and its turret ring was too small to accept a more powerful gun without extensive modification.
Australian crews bolted spare track links to the hull for extra protection, added suspension guards against jungle undergrowth, and fitted outside infantry telephones for ground troops. Engineers developed the Matilda Frog flamethrower variant, which saw action on Borneo, and the Matilda Hedgehog, armed with a seven-chambered spigot mortar, though the Hedgehog was completed too late to see combat.
The Red Army received 918 of the 1,084 Matildas sent to the USSR. Soviet crews used them from the Battle of Moscow onwards through 1942, but found the tank too slow and prone to suspension clogging from snow and dirt. Most Soviet Matildas were expended during 1942, with a small number serving on until 1944.
Around 70 Matilda IIs survive worldwide. The largest concentration, about 30, is in Australia, with five at the Royal Australian Armoured Corps Memorial and Army Tank Museum at Puckapunyal. The Tank Museum at Bovington in the United Kingdom has a fully restored running example and the only surviving Matilda Canal Defence Light. Other examples are held at the Kubinka Tank Museum in Russia, the Yad La-Shiryon museum in Israel, and the Musée des Blindés in France.